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APPLETONS' 
SCIENCE  TEXT-BOOKS. 


ANATOMY,  PHYSIOLOGY,  AND 
HYGIENE. 


General  Plan  of  the  Circulation. 


^pplctons'  Srimtt  Ctti-Jtoohs. 


THE  ESSENTIALS 


OF 


ANATOMY,  PHYSIOLOGY,  AND 
HYGIENE. 


A  TEXT-BOOK  FOR  SCHOOLS  AND  ACADEMIES. 


BY 

ROGER    S.    TRACY,   M.  D., 

SANITARY   INSPECTOR  OF  THE   NEW   YORK  CITY   HEALTH    DEPARTMENT  J 

AUTHOR  OF   "HAND-BOOK  OF   SANITARY   INFORMATION 

FOR   HOUSEHOLDERS." 


NEW   YORK: 

D.     APPLETON     AND     COMPANY, 

I,    3,    AND    5    BOND   STREET. 

1884. 


I 


Copyright,  1884, 
By  D.  APPLETON  AND  COMPANY. 


PREFACE. 


It  has  been  my  aim  in  preparing  this  volume  to 
compress  within  the  narrowest  space  such  a  clear 
and  intelligible  account  of  the  structures,  activities, 
and  care  of  the  human  system  as  is  essential  for  the 
purposes  of  general  education.  I  have  also  sought 
to  present  the  facts  and  principles  of  the  subject  in 
such  a  natural  order  as  will  best  subserve  the  true 
ends  of  scientific  education.  Useful  books  of  in- 
formation upon  physiology  are  already  numerous, 
but  they  are  too  generally  deficient  in  making  the 
science  valuable  as  a  means  of  mental  training.  Of 
course,  the  great  object  of  physiology  is  to  teach  how 
to  preserve  health,  but  this  is  not  best  done  by 
merely  memorizing  rules.  The  rules  must  be  sup- 
ported by  reasons,  and  if  there  is  not  some  thorough 
understanding  of  the  mechanism  and  powers  of  the 
human  body,  such  as  will  task  the  efforts  of  the 
student,  the  real  fruits  of  knowledge  will  not  be 
gained.  I  have  accordingly  given  prominence  to 
the  anatomical  and  physiological  facts  which  are 
necessary  preliminaries  to  instruction  in  hygiene, 
and  in  the  reasonings  upon  these  facts  I  have  aimed 
to  attract  and  interest  the  pupil,  to  teach  him  some- 
thing of  the  scientific  methods  of  approaching  the 


vi  PREFACE. 

subject,  and  to  connect  new  acquisitions  logically 
with  those  already  gained,  so  that  the  knowledge 
of  the  subject  may  become,  as  it  were,  organized 
into  faculty  in  the  minds  of  the  students.  So  im- 
portant has  it  seemed  to  me  to  impress  deeply  upon 
the  pupil's  mind  the  laws  of  connection  and  depend- 
ence among  the  various  parts  of  the  living  system 
that  I  have  thought  it  best  to  present  this  view,  in 
outline,  at  the  very  outset.  I  have,  therefore,  pre- 
fixed to  the  volume  a  General  Analysis,  which, 
while  it  serves  as  a  table  of  contents,  is  interspersed 
with  running  comments  explaining  the  general  re- 
lations of  the  different  organs  and  processes,  and  I 
recommend  that  this  analysis  be  carefully  read  by 
the  pupil,  so  that  he  may  become  familiar  with  its 
argument  before  proceeding  to  the  detailed  study 
of  the  text. 

One  of  the  greatest  modern  reforms  in  scientific 
study  is  undoubtedly  that  which  makes  it  more 
and  more  objective,  so  that  the  student  shall  con- 
stantly confirm  the  knowledge  he  gets  from  the 
book  by  reference,  as  far  as  possible,  to  the  objects 
themselves,  making  his  acquaintance  with  them 
direct,  and  his  information  real.  The  various  sci- 
ences lend  themselves  to  this  mode  of  study  in 
different  degrees ;  chemistry  and  physics  favoring 
experiment,  and  botany  offering  systematic  obser- 
vation more  than  any  other  scientific  subjects. 
Physiology  is  less  favorable  to  the  objective  method. 
For  the  purpose  of  ordinary  education,  it  must  be 
chiefly  taught  from  the  book,  with  such  accompani- 
ments of  lectures  and  illustrations  by  charts  as  the 
circumstances  will  allow.  But  even  here  much  may 
be  done  to  give  the  pupil  more  correct  ideas  of  the 


PREFACE.  vii 

elements  of  the  subject  than  can  be  obtained  from 
the  book  alone.  A  good  manikin  is  an  invaluable 
help  to  the  popular  study  of  anatomy  and  physiol- 
ogy. Human  dissection  being  out  of  the  question, 
the  manikin,  which  can  be  taken  to  pieces  so  as  to 
show  all  the  organs  in  their  situations,  connections, 
and  relative  dimensions,  will  afford  the  pupil  a  vivid 
and  exact  conception  of  the  dependent  parts  of  the 
living  body,  and  make  his  physiological  knowledge 
truthful  and  actual.  A  manikin  for  school  pur- 
poses costs  about  S25o,  and  may  be  imported  from 
Paris,*  where  they  are  made,  free  of  duty  for  educa- 
tional institutions. 

A  great  deal  is  also  to  be  learned  from  such 
rough  dissections  of  organic  tissue  and  structures 
as  may  be  made  anywhere.  Every  butcher's  shop 
is  full  of  specimens  of  all  parts  of  animals,  that  can 
be  cheaply  obtained  for  examination,  and  parents 
and  teachers  should  encourage  pupils  to  make  such 
rude  dissections  as  are  practicable,  and  will  help  to 
give  correct  ideas  of  the  relations  and  functions  of 
the  different  organs. 

The  study  of  the  minuter  parts  of  organized 
beings  with  the  microscope,  histology  as  it  is  called, 
has  come  into  great  prominence  in  modern  times, 
and  may  be  said  to  have  revolutionized  the  science 
of  life.  No  class  in  physiology  should  be  without  a 
microscope  for  the  direct  study  of  cell-structures 
and  the  finer  tissues  of  both  plants  and  animals.  A 
suitable  instrument,  with  a  magnifying  power  of 
three  hundred  and  fifty  diameters,  will  show  the 
circulation  in  the  web  of  a  frog's  foot,  and  open  a 
new  world  of  fascinating  and  wonderful  observation, 

*Auzoux  is  the  principal  manufacturer  of  these  models. 


vni 


PREFACE. 


while  it  may  be  bought  for  sixteen  dollars.  Micro- 
scopic preparations  of  blood-corpuscles,  muscular 
and  nervous  tissues,  and  sections  of  organs  may  be 
got  for  about  twenty  cents  apiece,  but  it  is  desirable 
that  the  pupil  should  not  rely  upon  these,  but  should 
learn  the  method  of  preparing  and  mounting  objects 
himself.  The  microscope  is  not  to  be  recommended 
as  a  mere  toy  to  amuse  idle  curiosity  ;  there  is  work 
connected  with  it  which  is  in  a  high  degree  educa- 
tional. It  cultivates  critical  observation  and  careful 
manipulation,  and  is  invaluable  as  a  means  of  self- 
education.  The  little  hand-book  of  Phin*  will  be 
found  useful  in  guiding  beginners  with  this  instru- 
ment . 

The  illustrations  are  largely  copied  from  Gray's 
"  Anatomy,"  though  I  am  also  indebted  to  Dalton's 
"  Physiology,"  to  Flint's  "  Physiology,"  to  Ranney's 
"Applied  Anatomy  of  the  Nervous  System,"  to 
Riidinger's  "  Topographisch-Chirurgische  Anato- 
mie,"  and  to  Neumann's  "  Hand-Book  of  Skin  Dis- 
eases." Many  of  the  figures  I  have  altered  to  suit 
my  purpose,  and  the  necessary  descriptions  are  so 
inscribed  upon  or  near  them  as  to  do  away  with 
the  inconvenience  of  lettered  references.  A  few  of 
the  cuts  are  original. 

For  the  use  of  material  other  than  the  illustra- 
tions, I  have  to  acknowledge  my  indebtedness  to 
Flint,  Beaumont,  Strieker,  Neumann,  Riidinger, 
Paget,  Maudsley,  Reynolds,  Aitken,  Huxley,  Soel- 
berg  Wells,  Uhle  and  Wagner,  Foster,  and  espe- 
cially to  Dalton. 

R.  S.  T. 

March  I,  1884. 
*  "A  Book  for  Beginners  with  the  Microscope,"  30  cents. 


GENERAL  ANALYSIS. 


Part  I.— Introduction. 

Gives  certain  necessary  definitions,  and  describes  the  cell 
and  its  properties  as  being  the  real  basis  of  all  more  fully 
developed  living  organisms. 

CHAPTER  PAGE 

I.  Definitions i 

II.  Minute  Structure  of  the  Body 3 

Part  II.— Organs  of  Motion. 

A  large  body  entirely  composed  of  cells  would  be  a  soft, 
jelly-like  mass,  incapable  of  locomotion  or  of  self-protection. 
But  to  obtain  food  it  must  be  able  to  move  from  place  to  place, 
and  also  to  move  its  different  parts  with  reference  to  one  an- 
other. For  these  purposes  there  must  be  points  of  resistance 
and  points  of  support.  These  points  are  furnished  by  the 
bones,  which  act  as  levers,  the  joints  being  the  fulcra. 

I.  Bones  in  General 9 

II.  Particular  Bones. — Joints 15 

III.  Injuries  of  Bones  and  Joints 25 

But  levers  alone  are  of  no  use.  The  bones  form  a  strong 
framework  for  the  body,  but  they  can  not  move  themselves. 
To  produce  motion,  organs  are  required,  which  can  become 
longer  or  shorter,  under  varying  circumstances.  Such  organs 
are  the  muscles. 

IV.  Muscles 29 


GENERAL  ANALYSIS. 


Part  III. — Organs  of  Repair. 

Energy  is  never  lost  or  created.  If  the  body  loses  energy 
in  one  way,  it  must  gain  it  in  another,  or  it  will  soon  be  worn 
out.  Every  muscular  contraction  wastes  a  certain  amount  of 
material,  and  an  equal  amount  must  be  again  supplied.  This 
is  done  in  the  form  of  food. 

CHAPTER  PAGE 

I.  Food. — Supply  and  Waste      ......    42 

But  food,  as  it  exists  outside  of  the  body,  can  not  be 
appropriated  by  the  wasting  tissues.  It  must  first  be  prepared. 
The  process  of  preparation  is  called  digestion. 

II.  Mastication. — Swallowing 50 

III.  Stomach-Digestion 57 

IV.  Intestinal  Digestion 79 

After  the  food  has  been  so  far  prepared,  it  must  in  some 
way  be  carried  through  the  body  to  all  its  different  parts,  that 
each  may  take  what  it  requires  for  its  sustenance.  This  is 
accomplished  by  means  of  a  fluid  which  passes  continually 
and  rapidly  through  all  parts  of  the  body,  carrying  the  nutri- 
tious material.     This  fluid  is  the  blood. 

V.  The  Blood 93 

But  the  blood,  besides  carrying  nutriment,  must  also 
remove  the  waste  and  used-up  matters,  which  injure  the  health 
if  they  remain  in  the  body.  There  is  also  a  gas,  called  oxygen, 
which  is  found  to  be  necessary  to  the  processes  of  nutrition. 
This  gas  exists  in  the  air,  and  is  taken  from  the  air  into  the 
blood.  The  process,  by  which  the  blood  gets  rid  of  impurities 
and  takes  in  oxygen,  is  called  respiration. 

VI.  Respiration 99 

VII.  Asphyxia 120 

The  blood  can  not  visit  the  different  parts  of  the  body  of  its 
own  accord.  It  is  a  fluid,  and  must  be  propelled.  There  are 
organs  for  this  purpose,  which  keep  up  what  is  called  the 
circulation  of  the  blood. 

VIII.  The  Heart 125 

IX.  The  Blood-Vessels  .        .        .        .        .        .        .        .  136 

X.  Disorders  of  Circulation. — Hemorrhage         .        .  150 


GENERAL   ANALYSIS. 


XI 


Part  IV.— Organs  of  Co-ordination. 

The  motions  of  the  body,  the  continual  waste  and  supply, 
and  the  processes  of  digestion  and  circulation,  form  a  very 
complicated  series  of  phenomena.  Certain  parts  of  the  body 
require  more  blood  at  certain  times  than  at  others.  Processes 
taking  place  at  the  same  time  in  different  parts  of  the  body 
might  conflict  and  interfere  with  each  other.  We  find,  there- 
fore, a  system  of  organs  whose  function  it  is  to  harmonize 
or  co-ordinate  all  these  processes,  to  produce  a  sympathy 
between  them,  and  make  them  all  work  together  for  the  com- 
mon interest.     This  is  the  nervous  system. 

CHAPTER 

I.  Nerve-Substance 
II.  The  Sympathetic  System 
III.  The  Spinal  Cord     . 


IV.  The  Brain 
V.  Special  Nerves. — Hygiene 

Part  V.— Organs  of  Protection. 

All  the  organs  previously  described  form  a  very  delicate 
structure,  which  is  continually  exposed  to  external  injurious 
influences.  It  is  exposed  to  heat  and  cold,  to  blows  and 
scratches,  and  all  manner  of  violence,  and  so  we  find  it  en- 
wrapped in  a  strong  covering,  which  protects  it  from  these 
influences,  partly  by  its  own  strength  and  toughness,  and 
partly  by  certain  organs  which  are  imbedded  in  it,  and  form 
a  part  of  it.  This  organ  is  the  skin,  with  the  various  glands 
and  other  structures  found  therein. 


PAGE 
I64 

174 
183 

194 
208 


I.  The  Skin 217 

II.  Functions  and  Care  of  the  Skin        ....  223 
Part  VI.— Organs  of  Perception. 

The  body  being  now  complete,  so  far  as  its  movements, 
nutrition,  co-ordination  of  parts,  and  protection  are  concerned, 
we  see  that,  as  its  food  must  come  from  outside,  there  must 
be  organs  to  bring  it  into  relation  with  the  external  world,  to 
aid  it  in  its  search  for  food,  and  to  protect  it  during  the  search. 
These  organs  are  the  organs  of  the  senses,  which  bring  us 
into  relation  with  what  is  outside  of  us.  and  in  this  way  are 
the  sources  of  our  ideas.  The  elementary  one  of  these 
senses  is  touch,  the  others  being  only  modifications  of  it. 


xii  GENERAL  ANALYSIS. 

CHATTER  PAGE 

I.  Touch,  Taste,  Smell 237 

II.  Hearing 246 

III.  Sight 254 

Part  VII. — Organ  of  Communication    .       .       .       .272 

The  body  being  now  practically  complete,  we  find  still 
another  organ,  whose  function  it  is  to  enable  us  to  communi- 
cate our  ideas  to  others.  This  organ  is  the  larynx,  the  organ 
of  speech,  that  wonderful  faculty  which  has  had  so  much  to 
do  with  creating  the  tremendous  gap  that  exists  between  man 
and  the  lower  animals. 

Questions 277 

Index 291 


PART     I. 

IN  TR  OD  UC  TION. 


CHAPTER  I. 

DEFINITIONS. 


1.  Definitions. — The  science  which  tells  us  about 
the  different  parts  of  the  body,  what  they  are,  where 
they  are,  and  how  they  look,  is  called  anatomy. 

The  science  which  tells  us  about  the  purpose  of 
these  parts,  what  they  do  and  how  they  do  it,  is 
called  pliysiology. 

The  science  which  tells  us  what  will  interfere 
with  the  working  of  these  parts,  what  will  injure 
and  what  will  help  them,  and  how  to  avoid  what 
is  hurtful,  is  called  hygiene. 

A  part  of  the  body,  which  is  so  small  that  when 
it  has  been  separated  from  other  parts  it  can  not  be 
further  subdivided  without  the  destruction  of  its 
organization,  is  called  an  anatomical  element,  as  a 
cell  or  a  fiber. 

Two  or  more  anatomical  elements,  united  or  in- 
terwoven so  as  to  form  one  substance,  make  what 
is  called  tissue  ;  e.  g.,  fatty  tissue,  connective  tissue, 
etc. 

A  part  of  the  body,  which  is  made  up  of  ana- 
tomical elements  and  tissues,  together  forming  one 


2  INTRODUCTION. 

whole,  which  can  be  separated  from  the  rest  of  the 
body  as  an  entire  mass,  and  which  performs  a  par- 
ticular function,  is  called  an  organ;  as,  the  liver, 
the  heart,  a  bone,  or  a  muscle. 

A  number  of  organs,  similar  in  structure,  but 
differing  in  size  and  shape,  and  spread  throughout 
the  body,  are  called  a  system ;  as,  the  nervous  sys- 
tem, the  arterial  system,  etc. 

Several  organs,  Avhich  differ  in  structure  but 
are  so  connected  as  to  work  together  for  a  particu- 
lar end,  are  called  an  apparatus ;  thus,  the  stomach, 
liver,  etc.,  constitute  together  the  digestive  appa- 
ratus. 

The  work  that  is  done  by  a  healthy  organ  in 
the  body  is  called  its  function ;  e.  g.,  the  secretion 
of  bile  is  a  function  of  the  liver. 


CHAPTER   II. 


MINUTE   STRUCTURE   OF  THE   BODY. 

2.  Minute  Structure  of  the  Body. — The  body, 
when  its  parts  are  examined  with  the  microscope,  is 
found  to  be  made  up  mainly  of  cells,  fibers,  and  fluids. 
The  cell  is  considered  to  be  the  original  element 
out  of  which  every  other  element  in  the  body  is 
formed ;  fibers,  fluids,  etc.,  being  derived  from  or 
generated  by  previously  existing  cells. 

The  different  consistency  of  different  organs  is 
due  to  the  varying  proportions  of  these  elements. 
If  the  fibers  are  in  the  largest  proportion,  the  tissue 
or    organ    will   be   hard, 
tough,  and  elastic  ;  if  the 
cells   form    the    greatest 
part,  it  will  be  soft,  inelas- 
tic, and  yielding. 

3.  The  Fiber.  —  The 
fiber  proper  (Fig.  1)  is  a 
slender  thread,  composed 
of  a  hard  whitish  or  yel- 
lowish substance,  some- 
times elastic  and  some- 
times not,  but  very  tough 

and  strong.     Fibers  are  found  in  almost  all  parts  of 
the  body,  binding  the  parts  of  organs  together,  and 


Fig.  i. — Fibrous  tissue. 


4  INTRODUCTION. 

constituting  almost  the  entire  mass  of  some  parts, 
as  the  tendons  or  sinews,  for  instance.  The  word 
"  fiber  "  is  also  used  of  certain  portions  of  muscular 
and  nervous  tissue,  in  a  different  sense  from  the  one 
given  above.  These  differences  will  be  explained 
hereafter. 

4.  The  Cell. — The  cell  is  the  most  important 
structure  in  the  living  body,  whether  animal  or 
vegetable.  Life  resides  in  the  cell ;  and  every 
plant  or  animal  may  really  be  looked  upon  as  a 
mass  composed  of  billions  of  cells,  each  of  which 
is  alive,  and  each  of  which  has  its  own  part  to  play 
in  the  nourishment  of  itself  and  the  rest  of  the 
body. 

A  single  cell  *  (Figs.  2  and  3)  is  a  portion  of  al- 


Fig.  2. — Epithelium  from  the  mouth. 


Fig.  3. — Liver-cells. 


buminous  matter,  which  has  by  some  been  called 
protoplasm,f  sometimes  surrounded  by  a  thin  mem- 

*  Scrape  gently  the  surface  of  the  tongue,  and  put  the  fluid  thus 
obtained  under  the  microscope.  Plenty  of  cells  will  then  be  seen, 
similar  in  appearance  to  those  shown  in  Fig.  2. 

f  Pro  loplasm,  from  two  Greek  words,  signifying  the  first  (or  primi- 
tive) formed  matter,  because,  so  far  as  we  know  at  present,  it  is  the 


MINUTE  STRUCTURE  OF    THE  BODY.  5 

brane  and  sometimes  not,  and  usually  having  in  its 
interior  what  looks  like  a  smaller  cell.  This  small 
body  is  called  the  nu'cleus  of  the  larger  one.  In- 
side of  the  nucleus  is  often  found  another  exceed- 
ingly minute  body,  or  sometimes  a  mere  shining 
point,  called  the  nucle'olus  (see  Fig.  52). 

5.  Protoplasm.  —  The  protoplasm,  or  matter 
which  forms  the  mass  of  a  cell,  is  of  a  semi-fluid 
consistency,  somewhat  like  jelly,  and  can  not  be  dis- 
tinguished by  chemical  tests  from  albumen.  Hence 
it  is  said  to  be  albuminous  in  its  nature,  resembling 
to  some  extent  the  white  of  a  raw  egg,  which  is 
almost  pure  albumen.  All  cells  are  so  exceedingly 
small,  being  rarely  more  than  10100  of  an  inch  in 
diameter,  that  we  really  know  very  little  of  their 
minute  structure,  on  account  of  the  difficulty  of  in- 
vestigating them  with  such  imperfect  instruments 
as  we  have. 

6.  Granular  Matter. — The  points  just  mentioned 
are  the  most  characteristic  of  the  cell.  Besides  the 
cells,  fibers,  and  fluids,  there  is  a  great  deal  of  mat- 
ter in  different  parts  of  the  body,  which  has  been 
formed  or  deposited  by  the  cells  at  different  periods 
of  their  growth.  This  matter,  under  the  micro- 
scope, sometimes  appears  granular,  or  as  if  made 
up  of  very  minute  specks,  and  sometimes  almost 
transparent.  Some  of  it  is  found  to  be  fat  in  a 
finely-divided  state,  but  some  of  it  is  albuminous, 
and  some  of  it  contains  mineral  matter  in  consider- 
able amount. 

7.  Difference  between  Living  and  Dead  Cells. — 
A  living  and  a  dead  cell  look  precisely  alike,  except- 

simplest  form  of  living  matter,  and  makes  up  the  only  part  of  all  ani- 
mal and  vegetable  bodies  which  shows  signs  of  life. 


INTRODUCTION. 


ing  that  the  dead  one  is  motionless.  A  living  cell, 
minute  as  it  is,  frequently  possesses  the  power  of 
independent  motion,  or  at  least  is  able  to  change 
its  form  (Fig.  4).  It  also  can  take  up  nourishment 
into  its  mass,  and  can  propagate  itself.  The  move- 
ments of  the  cell  can  be 
beautifully  seen  in  the 
white  cells  of  the  blood, 
which  will  be  described 
hereafter. 

8.  Growth  of  Cells. — 
A  cell  propagates  itself  in 
several  ways ;  one  of  the 
most  common  is  by  divid- 
ing into  two  parts.  This 
operation  has  been  often 
watched  under  the  micro- 
scope by  skilled  observers.  The  change  is  seen  to 
begin  in  the  nucleus,  and,  as  that  divides  by  a  line 
through  its  center,  the  protoplasm  of  the  cell  ar- 
ranges itself  in  halves  around  each  part  of  the  nu- 
cleus, its  surface  dipping  in  toward  the  center, 
until  finally  the  approaching  surfaces  meet  and  the 


Fig.  4. — White  cells  in  motion. 


Fig.  5. — Cell  dividing  and  forming  two  new  cells. 


cell  is  divided  into  two  new  cells,  each  with  its  nu- 
cleus, and  in  every  way  complete  (Fig.  5).  This 
division  goes  on  with  great  rapidity.  The  secre- 
tion from  the  throat  and  nose  in  nasal  catarrh  is 
composed  mainly  of  cells,  which  are  thrown  off  by 
millions  during  an  inflammation. 


MINUTE  STRUCTURE  OF   THE  BODY.  7 

9.  Other  Properties  of  Cells. — Cells  also  possess 
other  powers  which  enable  them  to  perform  their 
important  offices  in  the  body.  They  are  able  to 
select  certain  substances  out  of  a  general  mixture, 
and  reject  others.  This  is  done  by  the  liver-cells, 
for  example,  which  secrete  the  bile,  and  by  the  cells 
of  those  glands  which  secrete  the  saliva.  The  cells 
of  the  brain  act,  in  some  unexplained  way,  as  the 
instruments  of  thought.  The  cells  in  the  kidneys 
separate  matters  from  the  blood  which  are  very 
poisonous,  and  have  to  be  expelled  from  the  sys- 
tem. 

The  power  of  division  and  of  numerical  increase 
of  cells  is  not  unlimited.  If  a  portion  of  the  body 
is  wounded,  it  is  healed  again  by  the  active  efforts 
of  the  uninjured  cells  in  the  borders  of  the  wound. 
The  action  of  these  cells  ceases,  however  (if  the  part 
is  healthy),  to  reproduce  substance,  when  the  part 
made  vacant  by  the  injury  has  been  filled  up.  Why 
does  this  action  of  the  cells,  once  started,  not  con- 
tinue until  the  body  dies  ?  Why  does  the  replace- 
ment of  tissue  cease  as  soon  as  the  former  surface 
is  reached  ?  This  question  can  not  at  present  be 
answered.* 

Thus  we  see  that  the  cell,  minute  as  it  is  and 
simple  as  it  is,  performs  its  office  in  the  body  with 

*  When  the  cells  in  the  borders  of  a  wound  or  sore  are  not  in  a 
healthy  condition,  they  sometimes  increase  in  number  very  rapidly,  but 
the  new  cells,  instead  of  being  like  the  older  ones,  are  larger,  chiefly  ow- 
ing to  the  greater  amount  of  fluid  in  their  interior.  This  makes  them 
soft  and  spongy,  and  seems  to  interfere  with  their  functions.  They  do 
not  nourish  themselves  properly,  and  they  increase  and  grow  beyond 
the  limit  where  they  should  stop,  and  where,  if  they  were  healthy,  they 
would  stop.  This  unhealthy  growth  is  what  is  known  as  proud  flesh, 
and  it  has  to  be  repressed  by  proper  surgical  treatment. 


8  INTRODUCTION. 

care  and  evidence  of  forethought  and  intention.  It 
does  what  is  necessary  and  no  more.  It  does  not 
act  blindly.  It  does  all  it  does  with  a  purpose. 
Where  and  what  is  the  intelligence  that  directs  the 
active  living  cell  to  repair  so  far  and  no  farther,  to 
eat  this  and  reject  that,  to  multiply  up  to  a  certain 
point  and  then  stop,  and,  most  wonderful  of  all,  to 
take  upon  itself  the  duties  of  other  cells  when  they 
are  sick  and  unable  to  act,*  and  stop  performing 
these  extra  duties,  when  the  other  cells  recover  ? 

*  When  the  kidneys,  for  instance,  are  diseased,  so  that  the  excretion 
of  urine  is  interfered  with,  it  is  found  that  some  of  the  poisonous  mat- 
ters which  usually  pass  out  through  them  are  ejected  from  the  body 
through  the  lungs  and  skin.  In  such  cases,  physicians  try  to  assist  this 
process  by  inducing  active  perspiration,  so  as  to  relieve  the  kidneys 
from  work  as  much  as  possible,  and  allow  them  to  rest  until  they  get 
well. 


PART     II. 

ORGANS  OF  MOTION. 


CHAPTER   I. 

BOXES. — GENERAL  STRUCTURE. 

io.  Uses  of  the  Bones. — If  the  body  were  com- 
posed merely  of  cells,  such  as  have  been  described, 
with  fibers  and  fluids,  it  would  be  a  shapeless,  jelly- 
like mass,  incapable  of  locomotion,  and  of  self-pro- 
tection. There  is  a  necessity,  in  such  a  large  mass, 
of  points  of  support  and  resistance,  and  the  organs 
or  tissues  which  furnish  such  points  must  be  tough, 
hard,  and  elastic.  Such  organs  are  the  bones,  which 
form  the  framework  of  the  body  and  determine  its 
shape  and  size.  Their  most  important  offices  are 
two  in  number,  viz.,  to  act  as  levers  and  points  of 
support  and  action  for  the  muscular  parts,  and  to 
protect  the  soft  and  delicate  organs  from  external 
injury. 

ii.  Living  and  Dead  Bone.  —  A  bone,  as  we 
usually  see  it  outside  the  body,  is  as  different  from 
a  living  bone  as  the  skin  of  a  corpse  is  from  the  liv- 
ing skin.  We  usually  see  it  deprived  of  blood, 
while  in  the  living  body  it  is  full  of  it,  and  is  of  a 
pinkish-white  color  externally,  and  deep  red  within. 

12.  Composition  of  Bone. — To   accomplish   the 


10  ORGANS  OF  MOTION. 

two  purposes  above  mentioned,  bones  must  be  hard 
and  tough,  in  order  to  maintain  their  stiffness  when 
the  muscles  pull  upon  them,  and  also  to  be  able  to 
resist  external  blows.  They  must  also  be  in  some 
degree  elastic,  or  they  would  be  too  brittle  for  use, 
and  would  snap  in  two  under  great  pressure.  Ac- 
cordingly, we  find  all  bones  composed  of  two  kinds 
of  material,  so  thoroughly  mingled  and  united  that, 
when  either  kind  is  removed,  the  bone  still  retains 
its  peculiar  shape  and  size,  although  of  course  it 
does  not  weigh  as  much  as  before.  About  two 
thirds  of  the  weight  of  every  bone  in  the  adult  con- 
sists of  earthy  substances,  mostly  lime  phosphate 
and  lime  carbonate,  and  the  remaining  third  of  ani- 
mal matter,  part  of  which  can  be  separated  from 
the  rest  of  the  bone  by  long  boiling,  and  is  known 
as  gelatine. 

If  a  bone  be  burned  in  a  hot  fire,  all  of  the  ani- 
mal matter  will  be  destroyed,  and  the  earthy  mat- 
ters left.  These  will  still  retain  the  shape  of  the 
bone,  but  will  be  white  in  color,  and  will  easily 
break  and  crumble  in  the  fingers.  If  a  bone,  on 
the  other  hand,  be  soaked  for  a  time  in  dilute  hy- 
drochloric acid,  all  the  earthy  matter  will  be  dis- 
solved out,  and  the  animal  portion  left.  This,  as  in 
the  other  case,  will  retain  the  shape  of  the  bone, 
but  will  be  flexible  and  tough,  and  may  even  be 
tied  in  a  knot. 

By  the  combination  of  these  two  kinds  of  mat- 
ter, then,  the  bone  is  made  hard,  tough,  and  elastic, 
and  admirably  adapted  to  its  uses  in  the  body. 

13.  The  Composition  of  Bone  varies  with  Age. 
— In  infants  and  children,  the  amount  of  animal  mat- 
ter in  the  bones  is  proportionately  greater  than  in 


BONES.— GENERAL   STRUCTURE.  u 

the  adult,  and  so  the  bones  of  very  young  people 
will  often  bend  when  injured,  instead  of  breaking. 
Surgeons  call  this  the  "  green-stick  "  fracture,  be- 
cause the  bone  is  bent  like  a  green  twig,  only  a  small 
portion  of  it  on  the  outside  of  the  bend  being  broken 
or  torn  apart.  As  a  person  grows  older,  the  amount 
of  earthy  matter  increases,  until  in  old  people  the 
bones  become  very  brittle,  and  break  with  very 
slight  blows. 

14.  Varieties  of  Bone  and  their  Structure. — 
Bones  are  divided,  according  to  their  shape,  into 
long  bones,  short  bones,  flat  bones,  and  a  fourth  kind, 
called  irregular,  which  combine  qualities  belonging 
to  the  other  classes.  The  long  bones  are  found  only 
in  the  limbs,  and  are  the  most  important  to  the  sur- 
geon, as  it  is  in  them  that  most  fractures  and  other 
injuries  occur.  They  are  divided  into  a  shaft  and 
extremities.  The  shaft  of  every  long  bone  consists 
of  hard,  compact,  closely-grained  tissue,  somewhat 
like  ivory.  This  is  the  only  part  used  in  the  man- 
ufacture of  ornaments,  buttons,  knife-handles,  etc. 
The  extremities  of  these  bones  form  the  joints,  and, 
in  order  to  give  greater  security  and  a  greater 
purchase  to  the  muscles  as  well  as  a  greater  surface 
for  their  attachment,  the  ends  are  much  larger  than 
the  shaft.  The  tissue  of  which  they  are  composed 
is  also  not  so  hard  and  close  in  texture,  as,  if  it  were 
so,  the  bone  would  be  too  heavy.  There  is  no  finer 
example  of  economy  of  material  and  the  combina- 
tion of  strength  with  lightness  than  the  structure 
of  the  long  bones  (Fig.  6).  The  ends  are  made  of 
fine  threads  of  bone  interlaced  and  crossing  and 
supporting  each  other,  so  as  to  make  a  sort  of  spongy 
tissue,  full  of  little  cavities,  and  yet  very  strong  and 


12 


ORGANS  OF  MOTION. 


tough.    And  even  the  shaft  of  the  bone  is  not  solid, 
but,  as  every  one  knows,  is  hollow  in  the  middle. 

This  hollow  space  and  the  little 
cavities  of  the  ends  of  the  bone 
are  filled  with  what  is  called 
marrow,  a  substance  composed 
chiefly  of  blood-vessels  and  fat, 
which  has  important  duties  to 
perform  in  the  growth  and  nour- 
ishment of  the  bone.  The  other 
varieties  of  bone  are  composed 
entirely  of  the  spongy  (or  cancel- 
lous) tissue,  with  a  thin  layer  of 
hard,  compact  tissue  on  the  sur- 
face. 

15.  The  Periosteum  and  the 
Minute  Structure  of  Bone. — All 
the  bones  are  covered  with  a 
very  tough,  strong,  fibrous  mem- 
brane, called  the  periosteum,  ex- 
cepting at  the  parts  which  enter 
into  the  formation  of  the  joints, 
where  they  are  covered  with 
cartilage.  This  membrane  ad- 
heres so  closely  to  the  bone  as  to 
require  considerable  force  for 
its  separation.  It  seems  to  form 
a  part  of  the  bone.  Now,  the 
periosteum  and  the  marrow  of 
the  bones  are  necessary  to  their 
growth  and  nourishment.  The 
blood-vessels  and  nerves  spread  and  divide  in  these 
tissues  before  entering  the  actual  substance  of  the 
bone.     The  bone  itself  is  full  of  minute  channels  and 


Fig.  6.— The  right  femur, 
or  thigh-bone,  sawn  in 
two  lengthwise.  Notice 
the  arrangement  of  the 
bony  fibers  at  the  upper 
end,  its  peculiarity  be- 
ing somewhat  exagger- 
ated so  as  to  make  it 
more  plain. 


BONES.— GENERAL   STRUCTURE. 


13 


tubes  varying  in  size  from  -^-J-g-  to  the  So^00  of  an 
inch  in  diameter,  through  which  the  blood  cir- 
culates, and  the  smallest  of  these  tubes  are  con- 
nected at  one  end  with  exceedingly  minute  cavi- 
ties in  the  bone,  in  each  of  which  lies  a  little  cell, 
which  does  the  work  of  nourishing,  repairing,  and 

enlarging  the  bone 
(Fig.  7).     Thus  we 
see  that,  even  in  so 
hard  and  firm  a  tis- 
sue as  bone,  what 
has  been  said  about 
cells     holds     true. 
They  are  the  real 
life   of    the    bone ; 
they  separate  from 
the  blood  the  neces- 
sary  material   and 
deposit    it   around 
themselves,    some- 
what as  a  crab  re- 
news his  shell  eve- 
ry year   after  get- 
ting rid  of  the  old 
one. 
16.  Uses  of  the  Periosteum. — It  has  long  been 
known  that,  when  the  periosteum  is  severely  bruised 
and  separated  from  the  bone  by  violence,  the  por- 
tion of  bone  deprived  of  the  periosteum  dies  and 
has  to  be  removed  from  the  body.     It  is  also  found 
that  a  portion  of  bone,  or  even  an  entire  bone,  may 
be  removed  from  the  body,  and  if  it  be  carefully 
done,  so  as  to  leave  the  periosteum  in  its  place,  the 
bone  will  grow  again.     A  remarkable  example  of 
2 


Fig.  7. — Cross-section  of  bone,  magnified. 
The  small  black  spots  are  the  cavities  in 
which  the  bone-cells  live.  The  fine  lines 
are  canals  through  which  the  plasma  (sec- 
tion 122)  of  the  blood  passes.  The  large 
holes  are  for  blood-vessels. 


14 


ORGANS  OF  MOTION. 


this  was  a  case  operated  upon  by  the  late  Dr.  James 
R.  Wood,  of  New  York.  In  a  young  woman,  whose 
lower  jawbone  had  become  dead  and  caused  her 
great  suffering,  this  distinguished  surgeon  removed 
the  whole  jaw,  leaving  the  periosteum  and  even  the 
teeth,  held  in  their  places  by  an  apparatus  made  for 
the  purpose.  The  entire  bone  grew  again,  and  the 
teeth  became  fixed  in  it  as  it  grew.  The  person 
died  several  years  afterward,  and  her  skull,  show- 
ing the  result  of  this  wonderful  operation,  is  in  the 
museum  at  Bellevue  Hospital.* 

*  Other  experiments  have  even  shown  that,  if  a  piece  of  fresh  living 
periosteum  be  transplanted  from  a  bone  to  a  muscle,  it  will  produce 
bone  in  its  new  situation.  These  remarkable  qualities  of  the  perios- 
teum have  been  explained  by  some,  by  supposing  that,  in  each  case  of 
operation  or  experiment,  some  of  the  minute  bone-cells  have  adhered 
to  the  periosteum  when  the  mass  of  the  bone  was  removed,  and  that 
they  were  the  chief  agents  in  forming  the  new  bone. 


CHAPTER  II. 

NUMBER   OF   BONES. — PARTICULAR   BONES. — JOINTS. 

17.  The  number  of  bones  in  the  human  body  is 
two  hundred  (Fig-.  8).  At  one  period  of  life  they 
are  all  cartilaginous,  but  the  cartilage  gradually  be- 
comes changed  into  bone.  This  process  of  change, 
ossification,  as  it  is  called,  is  not  complete  before  the 
twenty-fifth  year  of  life,  and  therefore  no  person 
can  be  called  really  grown  up  until  that  time. 

18.  The  Vertebrae. — The  foundation,  so  to  speak, 
of  the  body — that  portion  of  the  skeleton  to  which 
the  remainder  is  attached,  and  from  which  it  is 
built  up — is  the  spine,  or  backbone  (Fig.  9).  This 
is  composed  of  many  small  bones,  all  of  the  same 
general  pattern,  called  vcr'tebrce.  The  principal  part 
of  the  vertebra  (Fig.  10),  called  the  body,  is  shaped 
very  much  like  a  wooden  pill-box  slightly  hollowed 
out  on  the  top  and  bottom.  The  bodies  of  the  ver- 
tebrae form  the  front  of  the  spinal  column.  From 
the  rear  of  each  of  these  bodies  are  offshoots  of 
bone,  which  unite  in  such  a  way  as  to  leave  a  hole 
about  half  an  inch  in  diameter  running  up  and 
down.  These  vertebrae  are  placed  one  above  an- 
other, with  elastic  pads  of  cartilage  between  their 
bodies.  These  pads  are  so  thick  that,  taken  all  to- 
gether, they  make  up  about  one  fourth  of  the  whole 


i6 


ORGANS  OF  MOTION. 


Fig.  8.— The  skeleton. 


THE  SPINE. 


17 


length  of  the  backbone.  The  vertebrae  being  ap- 
plied to  each  other  in  this  way,  it  is  evident  that 
the  holes  just  mentioned,  which 
are  surrounded  by  bone,  will  form 
a  continuous  canal  (the  spinal  ca- 
nal) running  from  the  skull  down 
the  back.  This  canal  contains 
the  spinal  cord,  which,  next  to  the 
brain,  is  the  most  important  part 
of  the  nervous  system.  At  the 
sides  of  the  spine,  throughout  its 
whole  length,  are  holes,  out  of 
which  pass  nerves  supplying  the 
muscles  and  other  organs  of  the 
body,  and  into  which  pass  the 
blood-vessels  that  nourish  the 
spinal  cord. 

19.  The  Spine. — The  back- 
bone, being  composed  of  so  many 
pieces,  is  very  movable.  The 
power  of  motion  varies,  however, 
in  different  parts.  It  is  greatest 
in  the  neck,  and  least  in  that  por- 
tion of  the  back  to  which  the  ribs 
are  attached.  In  the  human  be- 
ing, the  neck  is  not  so  flexible 
as  in  many  animals.  Birds,  in 
particular,  can  look  directly  back- 
ward. 


great 


fig.  9.-The  spine,  sawn  Notwithstanding     the 

in     two     lengthwise,  r  .  , 

showing   the   spinal  power  of  motion  in  the  spine,  the 

canal  and  the  holes  different  bones  are  very  strongly 

between     the     verte- 


united  and  protected  by  power- 
biood-vesseis pass  out.    ful  ligaments  and  muscles,  which 


brae,  where  nerves  and 


1 8  ORGANS  OF  MOTION. 

render  it  difficult  for  a  vertebra  to  slip  out  of  place, 
and  such  an  accident  is  one  of  the  rarest  which  a 
surgeon  is  ever  called  upon  to  treat. 


Fig.  io. — A  vertebra. 

The  elastic  pads  between  the  vertebrae  deaden  all 
shocks  of  the  body  and  prevent  them  from  injuring 
the  brain.  These  pads  become  compressed  during 
the  day,  especially  when  a  person  is  much  on  his 
feet,  so  that  at  night-time  the  body  is  from  one 
quarter  to  one  half  an  inch  shorter  than  it  is  in  the 
morning.  During  sleep  or  rest  the  elasticity  of  the 
pads  causes  them  to  resume  their  original  shape 
and  thickness. 

20.  The  Skull. — The  skull  is  the  only  portion  of 
the  skeleton  whose  principal  office  is  the  protec- 
tion of  soft  parts  within  it.     Accordingly,  we  find 


SUTURES  OF   THE  SKULL. 


19 


that  its  bones  are  differently  composed  and  dif- 
ferently put  together  from  the  other  bones  in  the 
body.  Those  forming  the  outside  of  the  skull,  im- 
mediately surrounding  the  brain,  and  most  exposed 
to  blows,  are  composed  of  three  layers.  The  out- 
side layer  is  the  thickest,  and  is  tough  and  some- 
what elastic.  The  innermost  layer  is  very  thin,  but 
hard  and  brittle,  so  that  it  is  called  the  vit'reous 
(glassy)  table  of  the  skull.  Between  these  layers  is 
spongy  tissue,  like  what  has  been  before  described. 
This  deadens  every  blow  upon  the  head,  and  the 
safety  of  the  brain  is  still  further  provided  for  by 
the  arched  shape  of  the  skull,  which  tends  to  dif- 
fuse the  force  of  a  blow.  The  protection  afforded 
by  the  shape  and  structure  of  the  outside  por- 
tion of  the  skull  is  very  great,  and  it  is  a  well- 
known  fact  in  surgery  that  a  blow  upon  the  top 
of  the  head,  without  breaking  the  bone  on  which 
it  falls,  may  break  the  bones  at  the  base  of  the 
skull,  immediately  opposite  the  spot  of  the  blow, 
by  the  mere  force  of  the  shock,  although  the  latter 
bones  are  much  thicker  and  more  massive  than  the 
others. 

There  is  only  one  movable  bone  in  the  skull  and 
that  is  the  lower  jaw.  If  the  upper  jaw  be  made  to 
move  in  eating  or  speaking,  it  is  only  by  moving 
the  whole  head  where  it  joins  the  neck. 

21.  Sutures  of  the  Skull. — The  bones  of  the 
skull  are  joined  together  by  what  are  called  sutures 
— i.  e.,  their  edges  are  jagged  and  irregular,  and  fit 
together  like  dovetailed  boards  (Fig.  11).  This 
renders  the  arch  of  the  skull  more  compact,  and, 
as  far  as  resistance  to  pressure  is  concerned,  the 
bones  might  be  considered  as  one  piece,  while  the 


20 


ORGANS  OF  MOTION. 


Fig.  ii.- 


-General  outlines  of  the  skull,  show- 
ing the  sutures. 


interruptions   at  the   sutures   tend   to  deaden  the 
shock  of  a  blow. 

22.  The  Frontal  Sinuses. — In  the  front  of  the 

skull  there  are  two 
cavities  in  the  sub- 
stance of  the  bone 
itself.  These  are 
situated  just  above 
the  eye-brows,  and 
are  called  the  fron- 
tal si'nuses  (Fig.  1 2). 
The  layer  of  bone 
which  forms  their 
front  wall  causes 
the  prominences 
just  over  the  eye- 
brows, and,  as  the  cavities  increase  in  size  with 
age,  this  portion  of  the  forehead  becomes  more 
prominent.  The  cavities  are  lined  with  mucous 
membrane,  and  are 
connected  with  the  in- 
side of  the  nose  by  a 
canal  or  small  passage, 
so  that,  when  a  person 
has  a  severe  cold  in 
the  head,  the  inflam- 
mationsometimes  runs 
up  this  passage  into 
the  frontal  sinuses. 
When  this  is  the  case, 
the  person  has  a  dull, 
stuffy  headache  in  that 
locality,  due  to  the  swelling  of  the  mucous  membrane. 

23.  The  Ribs. — The  bony  part  of  the  walls  of 


Fig.  12. — Frontal  sinus. 


NATURAL   SHAPE  OF   THE  CHEST.  2\ 

the  chest  is  made  up  of  twenty-four  ribs  and  the 
breast-bone,  together  with  part  of  the  spine  behind. 
There  are  twelve  ribs  on  each  side,  the  first,  nearest 
the  neck,  being  usually  the  shortest.  They  increase 
in  length  from  the  first  to  the  seventh,  and  then  di- 
minish, so  that  the  twelfth  is  also  quite  short.  They 
are  flat  and  narrow,  and  are  attached  at  one  end  to 
the  spine,  in  such  a  manner  that  they  move  easily 
up  and  down,  while  the  other  end  is  attached  to  the 
breastbone,  or  sternum,  by  means  of  a  piece  of  car- 
tilage, varying  in  length  with  the  length  of  the  rib. 
The  eleventh  and  twelfth  ribs  are  not  attached  to 
anything  at  their  forward  end,  and  hence  are  called 
floating  ribs. 

The  ribs  are  attached  to  the  spine  in  such  a  way 
that  all  of  them  move  together  up  and  down.  In 
front,  the  stiff  but  elastic  cartilage  allows  motion  in 
every  direction.  Now  the  shape  of  the  ribs  is  so 
peculiar,  being  a  sort  of  double  curve,  that  when 
they  are  raised  at  the  sides,  the  ends  which  join  the 
breastbone  are  pushed  forward,  and  of  course  carry 
the  breastbone  with  them.  So  it  is  evident  that  at 
every  inspiration  the  diameter  of  the  chest  increases 
from  front  to  rear  as  well  as  from  side  to  side. 

24.  Natural  Shape  of  the  Chest. — In  young  peo- 
ple the  cartilages  are  soft,  but  they  grow  harder  as 
age  advances,  and  become  partially  turned  into 
bone.  In  youth  they  yield  to  pressure  to  such  an 
extent  that  by  tight  lacing  the  shape  of  the  chest  is 
sometimes  made  exactly  the  reverse  of  what  it  ought 
to  be  (Fig.  1 3).  The  ribs  naturally  form  a  cone,  with 
the  smaller  end  uppermost,  but  it  is  not  uncom- 
mon to  see  the  smaller  end  at  the  waist.  Na- 
ture will  endure  a  great  deal  of  meddling,  but  it 


22 


ORGANS  OF  MOTION. 


is  not  always  safe  to  trifle  with  her,  and  all  persons 
who  carry  tight  lacing  too  far  will  inevitably  suffer. 


25.  The  Limbs. — More  than  one  half  of  the 
bones  in  the  body  are  found  in  the  limbs.  Out  of  two 
hundred  bones,  they  contain  one  hundred  and  twen- 
ty-six, and  these  are  so  constructed  and  so  arranged 
as  to  afford  a  great  variety  of  movement.     The  up- 


THE  JOINTS. 


23 


per  and  lower  limbs  are  what  is  called  homol'ogous 
in  their  parts — i.  e.,  each  bone  in  the  arm  has  its 
counterpart  in  the  leg,  with  only  slight  apparent 
exceptions.  Thus, 
the  shoulder  -  blade 
corresponds  to  the 
body  of  the  hip-bone, 
the  collar-bone  to  the 
front  of  the  hip,  the 
arms  to  the  thigh, 
the  two  bones  of  the 
fore-arm  to  the  two 
of  the  leg,  the  wrist 
to  the  ankle,  and  the 
hand  and  fingers  to 
the  foot  and  toes. 
The  similarity  and 
correspondence  of 
these  parts  are  quite 
clear  in  the  skeleton. 
26.  The  Joints. — 
To  render  move- 
ments possible,  the 
skeleton  is  broken  up 
in  its  whole  extent 
by  numerous  joints. 
The  surfaces  of  the 
joint  are  not  covered 
by  periosteum,  but 
by  a  firm,  bluish- 
white,  smooth,  and 
very  elastic  sub- 
stance called  carti- 
lage.    The  two  cartilage-covered  surfaces  in  every 


1 


Fig.  14. — The  right  knee-joint,  showing  how 
strongly  it  is  bound  about  by  ligaments. 


24 


ORGANS  OF  MOTION. 


joint  are  in  contact  with  each  other.  The  joint  is 
closed  entirely  by  the  syno' vial  membrane,  which 
passes  over  from  one  bone  to  the  other,  all  round 
the  outside.  This  membrane  is  exceedingly  smooth 
and  delicate,  and  its  inner  surface  exudes  a  fluid  very 
much  like  the  white  of  an  eggf  which  moistens  the 
surface  of  the  joint  and  renders  every  movement 
easy  and  frictionless.  Outside  of  these  structures 
are  ligaments  (Fig.  14),  which  hold  the  bones  firmly 
in  their  places.  Ligaments  are  composed  of  white, 
fibrous  tissue  (Fig.  1) — i.  e.,  of  tough,  inelastic  fibers 
or  threads  running  parallel  with  each  other,  of  a 
shining,  silvery-white  color.  They  are  flexible,  so 
as  to  allow  of  considerable  lateral  movement,  but 
are  tough  and  exceedingly  strong,  so  that  they  hold 
the  ends  of  the  bones  close  together.  Thus,  the 
construction  of  the  joints  is  such  that  they  are 
strong,  flexible,  elastic,  and  supple. 


CHAPTER   III. 

INJURIES   OF  BONES   AND   JOINTS. 

27.  Injuries  in  General. — The  injuries  to  which 
the  bones  are  most  liable  are  fractures  and  disloca- 
tions. If  the  bone  be  fractured,  the  jagged  ends  of 
the  broken  bone  irritate  the  parts  about  them,  and 
the  muscles  contracting  pull  the  broken  ends  out  of 
their  proper  relation  to  each  other  (Fig.  15).  In  the 
dislocation,  the  end  of  the  bone  is  out  of  its  proper 
place.  But  the  limb  is  movable  at  the  point  of  fract- 
ure, while  it  is  always  stiff  and  fixed  at  the  point 
of  dislocation.  In  a  fracture,  also,  the  ends  of  the 
bone,  if  gently  moved  against  each  other,  produce 
a  peculiar  grating  feeling,  which  always  tells  the 
surgeon  with  certainty  that  the  limb  is  broken. 

28.  Fractures. — Bones  are  rarely  broken  straight 
across,  excepting  in  very  young  persons.  The  fract- 
ure is  usually  oblique,  and  so  the  broken  ends  slide 
past  each  other,  and  the  limb  is  shorter  than  it  was 
before  the  accident.  In  a  broken  thigh,  the  bone  is 
surrounded  by  such  a  thick  mass  of  muscles  that, 
even  if  the  broken  ends  are  pulled  by  force  into 
their  proper  places,  it  is  impossible  to  keep  them 
there.  They  will  always  slide  past  each  other  to  a 
slight  extent,  and  a  person  never  recovers  from  such 
an  accident,  without  having  the  injured  limb  from 


26 


ORGANS  OF  MOTION. 


half  an  inch  to  an  inch  shorter  than  the  sound  one. 
This  has  been  shown  and  proved  by  thousands  of 

careful     measurements, 


DEL- 


TOID 


and  should  always  be 
borne  in  mind  when 
there  is  a  temptation  to 
blame  a  surgeon  for  fan- 
cied neglect. 

When  a  fracture  oc- 
curs near  a  joint  it  is  a 
much  more  serious  ac- 
cident, for 'the  inflam- 
mation which  follows 
the  injury  involves  the 
parts  about  the  joint, 
and  sometimes  the  joint 
itself,  which  maybe  left 
stiff  and  almost  useless 

Fig.  15.— Fractured  humerus,  showing     f or    a   \ong     time     after- 
how  the  muscles  pull  the  ends  of  the  -,         rpi   •  .• 

"  .     ,  /,  ,  ward.     This  is  particu- 

broken  bone  out  of  place.  r 

larly  the  case  with  frac- 
tures near  the  wrist,  for  the  slow  recovery  of  which 
the  surgeon  is  so  often  blamed. 

29.  Dislocations.  —  When  a  bone  is  dislocated 
there  is  always  a  certain  amount  of  injury  to  the 
parts  about  the  joint.  The  ends  of  the  bone  are  so 
carefully  and  strongly  guarded  and  fastened  by  lig- 
aments and  muscles,  that  these  must  necessarily  be 
considerably  torn  and  bruised,  in  order  to  let  the 
bone  out  of  its  place.  Thus  it  happens  that  a  dis- 
location often  gives  rise  to  more  pain  and  suffering 
immediately  after  the  accident  than  a  fracture * 

*  Sometimes  the  violence  resulting  from  a  fall  is  not  sufficient  either 
to  break  or  dislocate  a  bone,  and  yet  the  parts  about  a  joint  are  so  se- 


INJURIES  OF  BONES  AND  JOINTS.  2J 

The  vast  majority  of  dislocations  occur  in  the 
shoulder  and  hip  joints,  and  are  usually  caused  by 
a  blow  on  the  end  of  the  bone  when  the  limb  is 
firmly  extended,  as  when  a  person  is  falling  and  tries 
to  save  himself  by  stretching  out  his  hand.  The 
lower  jaw  is  sometimes  dislocated,  and  then  the 
mouth  remains  wide  open  until  the  dislocation  is 
reduced,  rendering  the  sufferer  a  somewhat  ludi- 
crous as  well  as  pitiable  sight.  This  accident  has 
been  known  to  occur  during  a  prolonged  yawn. 

30.  Healing  of  Injured  Bones. — A  fractured  bone 
takes  from  three  to  six  weeks,  and  sometimes  longer, 
to  become  healed.  A  dislocated  bone,  after  it  is  re- 
duced, requires  to  be  kept  quiet  until  all  pain  and 
swelling  have  subsided.  In  either  case,  there  always 
remains  more  or  less  stiffness,  which  sometimes 
does  not  disappear  for  months  after  the  accident. 

31.  Care  of  Injured  Persons. — It  frequently  hap- 
pens that  a  bone  is  broken  when  the  person  is  at  a 
distance  from  his  home,  or  from  any  place  where 
he  can  be  attended  by  a  surgeon.  In  fractures  of 
the  lower  limbs,  he  must  be  carried  often  for  a  long 
distance,  and  every  one  should  know  how  to  make 
him  comfortable  during  transit.  It  must  be  remem- 
bered that  the  only  object  of  any  person  who  is  not 
a  surgeon,  should  be  to  keep  the  broken  limb  in 
such  a  position  that  there  will  be  no  motion  of  the 
fractured  ends,  so  that  the  patient  may  suffer  as 
little  as  possible,  and  the  surgeon  may  find  him  as 
nearly  as  may  be  in  the  condition  in  which  the  in- 

verely  strained  that  some  of  the  ligaments  are  torn  apart.  Very  often 
only  a  few  fibers  are  ruptured,  but  such  injuries  always  cause  great  suf- 
fering, and  recovery  is  very  slow.  This  form  of  injury  is  called  a 
sprain,  and  is  most  likely  to  occur  in  the  wrist,  ankle,  or  knee. 


28  ORGANS  OF  MOTION. 

jury  left  him.*  Therefore,  he  should  be  carried  on 
a  litter,  the  broken  limb  being  packed  about  with 
soft  materials  in  such  a  way  as  to  keep  it  from  roll- 
ing or  jarring.  The  weight  of  the  foot  will  often 
make  the  lower  part  of  the  leg  swing  from  side  to 
side,  and  in  the  case  of  a  fractured  thigh,  the  leg 
should  be  protected  on  each  side  from  the  hip 
down.  Dislocations  require  the  same  care,  except- 
ing that  a  splint  is  not  necessary. 

*  It  is  a  very  good  plan  to  bind  the  lower  limbs  together  in  such  a 
case,  above  and  below  the  injured  part,  so  that  the  sound  leg  may  serve 
as  a  splint  to  the  broken  one.  A  broken  arm  may  be  bound  to  an  im- 
provised splint  (a  cane,  a  stick  of  wood,  a  shingle),  a  folded  handker- 
chief or  other  padding  being  used  to  fill  up  the  hollows  between  the 
splint  and  the  skin,  and  the  broken  limb  being  supported  by  a  sling 
around  the  neck. 


CHAPTER  IV. 

MUSCLES. 

32.  The  Muscles. — The  bony  framework  of  the 
body  is  set  in  motion  by  a  system  of  organs  called 
muscles,  which  cover  the  skeleton  almost  entirely 
(Fig.  A),  and  cause  the  different  bones  to  move 
upon  each  other  by  means  of  their  peculiar  prop- 
erty of  contractility,  or  the  power  of  becoming 
longer  or  shorter  under  varying  circumstances. 

There  are  two  kinds  of  muscles  in  the  body, 
called  voluntary  and  involuntary,  which  differ  very 
much  in  their  structure  and  functions.  The  volun- 
tary muscles,  as  the  name  implies,  are  under  the  con- 
trol of  the  will ;  while  the  involuntary  muscles  are 
not  only  beyond  our  control,  but  act  as  a  rule  with- 
out our  knowledge  or  consciousness. 

33.  The  Voluntary  Muscles. — A  voluntary  muscle 
is  a  mass  of  reddish  fibers,  somewhat  loosely  joined 
together  by  connective  tissue,  and  easily  separated 
lengthwise.*  The  flesh  of  animals  is  composed  of 
muscular  tissue.     Every  voluntary  muscle  is  united 

*  If  the  fibers  of  a  piece  of  lean  meat  are  carefully  separated  and 
closely  scrutinized,  it  will  be  seen  that  they  are  connected  with  each 
other  by  a  delicate  tissue  of  fine  white  threads,  interwoven  like  the 
fibers  of  a  cobweb  or  of  the  most  delicate  lace-work.  This  is  called 
connective  tissue,  and  is  found  in  almost  all  parts  of  the  body,  uniting 
the  different  elements  that  make  up  the  various  organs. 


30 


ORGANS  OF  MOTION. 


Fig.  A. — The  muscular  system. 


THE  MUSCLES. 


31 


at  each  end  to  some  fixed  point  in  the  body,  and 
there  is  always  a  joint  or  point  of  flexure  between 
its  points  of  attachment.  When  the  muscle  con- 
tracts, therefore,  the  two  ends  are  brought  nearer 
together,  and  motion  is  produced  in  the  organ  or 
limb  to  which  it  is  attached. 

Every  voluntary  muscle  can  be  divided  into 
small  fibers,  lying  side  by  side,  and  these  again  into 
fibrils  still  more  minute.  Each  fibril  under  the 
microscope  presents  an  appearance  of  delicate  lines 
running   at   right   angles   to   its   length    (Fig.    16). 


Fig.  16. — Voluntary  muscular  tissue. 

These  lines  are  called  stria,  and  the  appearance  is 
called  striation. 

34.  The  Involuntary  Muscles. — Involuntary  mus- 
cles are  made  up  of  flattish  bands  of  long,  narrow 
fibers,  tapering  at  each  end,  somewhat  of  the  shape 
of  an  oat,  but  more  slender.  Each  fiber  has  a  nu- 
cleus  in   its  middle,  and    they  are   all   connected 


32 


ORGANS  OF  MOTION. 


together    lengthwise,   as    the    voluntary   muscular 
fibers  are  (Fig.  17). 

35.  Differences  between  the  Voluntary  and  In- 
voluntary Muscles. — The  voluntary  muscles  are  all 
composed  of  the  striated  muscular 
fiber  which  allows  of  very  rapid 
contraction,  while  the  involuntary 
muscular  fibers  contract  in  a  very 
peculiar  manner.  They  do  not  be- 
gin to  contract  immediately,  as 
soon  as  they  are  stimulated,  but 
there  is  a  short  interval  between 
the  irritation  and  the  response  of 
the  muscle.  Then  the  contraction 
begins,  and  proceeds  slowly  and 
continuously  up  to  a  certain  de- 
gree, when  the  fibers  slowly  relax, 
very  much  like  the  slow,  crawling 
motion  along  the  body  of  a  worm 
or  snake,  when  a  wave  seems  to 
travel  from  one  end  to  the  other. 
Now  there  are  some  organs  in  the 
body,  whose  action  must  be  rapid,  from  the  nature 
of  the  office  they  perform,  and  still  it  would  not  do 
to  have  their  motions  depend  upon  the  will.  Such 
an  organ  is  the  heart.  It  must  contract  often  and 
quickly  in  order  to  supply  sufficient  blood  to  the 
body,  and  yet,  if  its  action  depended  upon  our  will, 
it  would  require  all  of  our  attention,  to  the  exclu- 
sion of  everything  else.  Accordingly,  we  find  it 
composed  of  muscular  fibers  that  are  intermediate 
in  structure  between  the  voluntary  and  involuntary 
kinds.  The  involuntary  muscular  fiber  is  found, 
among  other  places,  in  the  stomach  and  intestines, 


Fig.  17. — Involuntary- 
muscular  tissue. 


THE  MUSCLES. 


33 


in  the  iris  of  the  eye,  and  in  the  walls  of  the  ar- 
teries. 

36.  Difference  in  Size  of  Muscles. — The  largest 
muscle  of  the  back,  the  latissimus  dorsi,  weighs  sev- 
eral pounds ;  and  one  of  the  muscles  of  the  leg,  the 
sartorius,  is  two  feet  long  ;  while  the  stapedius,  one  of 
the  little  muscles  inside  the  ear,  is  only  the  sixth  of 
an  inch  long,  and  weighs  about  a  grain.*  Between 
these  extremes  are  many  variations  in  size  and 
shape. 

37.  The  Tendons. — Muscles  are  connected  with 
the  bones  by  means  of  tendons.  A  tendon  is  made 
up  of  fibrous  tissue,  and  is  a  white,  glistening  cord, 
of  exceeding  strength  and  toughness.  At  the  ends, 
they  gradually  change  their  appearance,  becoming 
muscle  at  one  extremity  and  bone  or  periosteum 
at  the  other.  There  is  no  sharp  line,  where  the 
muscle  or  bone  can  be  distinguished  from  the  ten- 
don. Wherever  the  tendons  would  be  likely  to  rise 
and  form  a  line  like  the  string  of  a  bow  during  the 
contraction  of  a  muscle,  as  at  the  wrist  and  the 

*  Latissimus  dorsi — i.  e.,  the  broadest  of  the  back.  This  muscle  is 
attached  to  the  spine  in  the  lumbar  region  and  also  to  the  lower  ribs. 
The  fibers  come  together  so  that  the  muscle  has  a  triangular  shape,  and 
its  small  end  is  attached  to  the  humerus.  It  is  the  chief  muscle  that 
comes  in  play  when  the  body  is  raised  from  the  ground  by  means  of  the 
arms. 

The  sartdiius  means  the  tailor's  muscle.  It  is  a  long,  ribbon-like 
muscle,  which  begins  on  the  outside  of  the  hip-bone  and  ends  on  the 
inside  of  the  knee,  crossing  the  thigh  on  the  inner  side.  When  it  con- 
tracts, it  raises  the  lower  part  of  the  leg,  and  turns  it  inward,  thus 
crossing  the  legs,  tailor-fashion — hence  its  name.  It  comes  in  play 
when  one  foot  is  placed  on  the  opposite  knee. 

Stapedius  means  the  stirrup-muscle,  so-called  because  it  is  attached 
to  a  small  bone  in  the  ear,  which  is  shaped  like  a  stirrup,  and  hence 
called  stapes  (Latin  for  stirrup). 


34  ORGANS  OF  MOTION. 

ankle,  for  example,  they  are  bound  down  by  stout 
ligaments,  through  or  under  which  they  slide  to  and 
fro,  the  channels  in  which  they  move  being  lined 
with  synovial  membrane  like  the  joints. 

38.  Force  of  Muscular  Contraction.  —  When  a 
muscle  contracts  (whether  voluntary  or  involuntary), 
it  becomes  not  only  shorter  and  thicker,  but  harder, 
than  before,  and  the  force  with  which  it  contracts 
is  enormous.  To  attain  the  compactness  which  we 
see  in  the  body,  the  muscles  of  the  limbs,  for  ex- 
ample, have  to  lie  parallel  with  the  length  of  the 
limb.  Besides  this,  many  of  them  are  attached  be- 
tween the  fulcrum  and  the  weight,  and  very  near 
the  fulcrum.  The  biceps,  for  instance,  which  (with 
the  brachialis  anticus)  bends  the  forearm  upon  the 
arm,  is  attached  at  one  extremity  to  the  shoulder- 
blade,  and  at  the  other  to  the  forearm,  just  below 
the  elbow,  where  its  tendon  can  be  felt.  Thus  there 
are  two  disadvantages  under  which  it  acts.  In  the 
first  place,  its  point  of  action  is  only  about  one  eighth 
as  far  from  the  joint  or  fulcrum  as  the  hand  is,  and 
in  the  second  place,  when  it  begins  to  contract,  it 
acts  at  a  very  acute  angle — in  fact,  almost  parallel 
with  the  bone  (Fig.  18).    As  the  arm  becomes  flexed, 


Fig.  18. — Disadvantageous  action  of  the  biceps  muscle, 
illustrated. 

the  angle  of  action  approaches  more  and  more  to  a 
right  angle,  and  the  necessary  effort  becomes  less 


THE  MUSCLES. 


35 


and  less.  And  yet  we  not  only  flex  the  arm  easily 
enough  at  the  elbow,  but  we  do  it  with  a  consider- 
able weight  in  the  hand.  It  has  been  estimated  that 
the  muscles  of  the  arm,  in  flexing  it  at  the  elbow, 
with  a  ten-pound  weight  in  the  hand,  contract  with 
a  force  of  at  least  two  hundred  pounds.  And  yet 
this  is  a  feat  which  a  delicate  woman  or  a  child  can 
perform,  and  the  force  required  is  not  to  be  com- 
pared with  the  power  of  an  athlete. 

39.  Muscular  Irritability.  —  Muscular  tissue  will 
contract  under  any  kind  of  irritation.  In  the  living 
body,  the  stimulus  always  comes  from  the  nerves, 
but  the  muscle  itself  has  a  form  of  irritability,  which 
lasts  for  a  considerable  time  after  death.  When  an 
ox  is  killed,  and  has  been  prepared  for  the  market, 
the  muscles  may  often  be  seen  twitching  and  quiver- 
ing in  the  beef  for  half  an  hour,  and  the  muscles  of 
an  amputated  arm  may  also  be  seen  to  contract  for 
some  minutes  merely  under  the  irritation  of  the  cold 
air.  In  cold-blooded  animals,  this  irritability  persists 
for  a  long  time.  If  the  heart  of  a  frog  be  entirely 
removed  from  the  body,  it  will  continue  to  beat  for 
several  minutes,  and,  when  it  has  finally  ceased,  it 
will  start  again  on  being  pricked  with  a  needle. 
This  experiment  may  be  repeated  several  times  be- 
fore the  muscular  irritability  finally  vanishes.* 

40.  The  Muscular  Sense. — When  a  muscle  con- 
tracts, the  degree  of  contraction  is  perceived  or  felt 

*  There  are  reasons  for  believing  that  the  continued  beating  of  the 
heart  of  a  cold-blooded  animal  for  hours  after  it  has  been  removed 
from  the  body  may  be  due  to  the  presence  of  microscopic  nervous 
ganglia  in  the  substance  of  the  muscle.  This  supposition,  however, 
does  not  affect  the  usefulness  of  the  frog's  heart  as  an  illustration  of 
the  fact  that  parts  of  animals  continue  to  live  after  separation  from  the 
main  body. 


36  ORGANS  OF  MOTION. 

by  the  brain.  For  example,  any  one  is  conscious 
whether  his  thumb  is  bent  inward  toward  the  hand, 
or  outward  toward  the  wrist,  entirely  apart  from 
the  use  of  the  sight.  The  precise  manner  in  which 
this  sensation  is  conveyed  to  the  brain  is  still  a  sub- 
ject of  conjecture.  Although  apparently  so  simple, 
it  brings  up  questions  of  great  intricacy  and  dif- 
ficulty, which  can  not  be  considered  here.  But  this 
sense,  whatever  its  manner  of  operation,  is  called  the 
muscular  sense.  It  is  one  of  the  chief  means  we  have 
of  determining  the  wTeight  or  the  hardness  and  soft- 
ness of  bodies,  as  we  judge  of  these  qualities  mainly 
by  the  resistance  our  muscles  meet  with  when  hand- 
ling the  bodies.  But,  more  than  all,  the  muscular 
sense  is  necessary  in  keeping  the  body  upright.  The 
size  of  the  feet  is  so  small,  compared  with  the  height 
of  the  body,  that  early  in  life  it  is  a  matter  of  ex- 
treme difficulty  for  us  to  keep  our  balance.  To 
stand  and  walk  is  one  of  the  first  and  one  of  the 
hardest  things  Ave  have  to  learn.  It  requires  a  con- 
stant contraction  of  the  muscles,  now  one  set  and 
now  another,  in  order  to  keep  from  falling. 

41.  Use  of  the  Muscular  Sense  in  Standing. — 
Ordinarily  we  are  assisted  in  standing  upright  by  our 
sight.  This  fact,  together  with  the  muscular  effort 
required  to  stand  still,  may  both  be  made  very  evi- 
dent in  the  following  manner:  if  a  person  stands 
with  the  feet  close  together,  he  will  perhaps  feel  a 
slight  swaying  of  the  body,  which  has  to  be  counter- 
acted by  muscular  contraction.  Perhaps  no  such 
swaying  will  be  perceptible  to  him.  But  now,  still 
keeping  the  feet  close  together,  let  him  shut  the 
eyes,  when  the  swaying  of  the  body  will  become 
much  greater  than  before,  and  the  constant  muscular 


THE  MUSCLES. 


37 


contractions,  now  here,  now  there,  will  be  so  plainly- 
felt  as  to  be  disagreeable.  In  certain  diseases,  this 
muscular  sense  in  the  legs  is  lost,  and  then  the  per- 
son can  stand  with  the  eyes  open,  but  if  the  eyes  be 
closed  he  instantly  totters  and  falls,  for  he  then  has 
nothing  to  guide  him  as  to  his  vertical  position. 

42.  Waste  during  Muscular  Contraction. — The 
cause  of  muscular  contraction  is  an  unsolved  prob- 
lem. There  is  nothing  in  the  chemical  composition 
or  the  physical  structure  of  the  muscle  which  would 
lead  us  to  expect  to  see  it  contract  when  irritated, 
if  we  knew  nothing  more  about  it.  All  we  can  say 
is,  that  it  depends  upon  the  composition  of  the  mus- 
cular substance,  and  we  know,  also,  that  every  con- 
traction is  accompanied  by  a  loss  of  or  change  of 
material.  In  this  way,  our  muscles  are  being  con- 
tinually used  up,  and  if  they  were  not  constantly  sup- 
plied with  fresh  nourishment  by  the  blood,  they 
would  soon  wear  out  and  die.  But  the  minute  mus- 
cular fibers  (or  the  cells  composing  them)  not  only 
perform  their  special  function  of  contraction,  but 
are  able  to  choose  and  take  up  out  of  the  blood  their 
own  proper  food  and  appropriate  it. 

43.  Muscular  Overwork. — If  a  muscle  is  hard 
pressed  and  exercised  too  much,  so  that  the  waste 
of  material  is  greater  than  the  supply,  and  it  wears 
away  faster  than  it  is  repaired,  it  falls  into  the  con- 
dition which  we  call  fatigue,  and  it  is  only  with 
great  effort  that  we  can  make  it  work.  If  it  be  still 
further  imposed  on,  without  opportunity  to  recu- 
perate, it  soon  gives  out  entirely,  and  can  not  be 
made  to  contract  with  vigor  under  any  stimulus  our 
brain  can  send  to  it.  Such  extreme  fatigue  is  dan- 
gerous, because  there  is  always  the  chance  that  the 

3 


38  ORGANS  OF  MOTION. 

muscular  fibers  may  become  so  completely  wasted 
that  even  their  power  of  nourishing  themselves  may 
be  impaired,  and  the  recovery  of  their  natural  con- 
dition may  be  very  slow  and  imperfect,  or,  in  rare 
cases,  impossible. 

44.  Muscular  Inactivity. — On  the  other  hand,  if  a 
muscle  is  not  exercised  at  all,  its  power  of  nourish- 
ing itself  is  interfered  with  almost  as  much  as  if  it  is 
exercised  too  much.  It  is  found  that  unused  mus- 
cles gradually  waste  away,  growing  smaller  and 
smaller,  and  becoming  soft  and  flabby,  and  finally,  if 
they  are  not  used  for  a  very  long  time,  it  can  be  seen 
by  the  microscope  that  the  muscular  fibers  disappear 
altogether,  or  are  filled  with  little  particles  of  fat, 
which  take  the  place  of  some  of  the  muscular  sub- 
stance, and  so  make  it  very  weak  and  useless.  Such 
inactivity  of  the  muscles  may  occur  in  cases  of  paral- 
ysis, and  the  physician  is  then  careful  to  stimulate 
them  with  electricity,  in  order  to  keep  them,  as 
nearly  as  possible,  in  a  sound  condition.  The  elec- 
trical current,  in  such  cases,  takes  the  place  of  the 
nervous  stimulus,  which  naturally  causes  muscular 
contraction.  The  muscles  of  a  broken  limb,  also, 
which  have  necessarily  been  idle  while  the  bone  was 
mending,  are  always  very  feeble  for  some  time  after 
the  limb  comes  in  use  again.* 

*  Curvature  of  the  spine,  which  is  more  frequent  among  girls  than 
among  boys,  is  often  directly  attributable  to  lack  of  exercise.  The 
muscles  of  the  back  become  weak,  and,  as  some  exercise  of  the  muscles 
of  the  right  side  can  not  be  avoided,  so  long  as  the  girl  performs  any 
duties  whatever,  the  difference  in  strength  between  the  muscles  of  the 
right  side  and  those  of  the  left  side  becomes  greater  than  is  natural. 
The  result  of  this  is  that  the  stronger  muscles  overpower  the  others  and 
pull  the  spine  over  toward  the  right  side,  greatly  distorting  the  figure. 
In  left-handed  persons  the  curvature  is  toward  the  left  side. 


EXERCISE.  39 

45.  Exercise. — It  is  necessary,  therefore,  that  the 
muscles  should  be  sufficiently  exercised,  and  not  too 
much.  The  kind  of  exercise  is  not  of  so  much  im- 
portance. No  better  form  of  exercise  can  be  de- 
vised than  the  various  out-door  sports  that  boys  are 
so  fond  of.  It  is  much  better  that  exercise  should 
be  a  pleasure  than  a  duty.  For  this  reason,  the  or- 
dinary exercises  of  the  gymnasium  do  not  compare 
in  value,  as  health-giving  ones,  with  rowing,  skating, 
running,  riding,  wrestling,  swimming,  and  the  va- 
rious out-door  games.*  It  is  really  of  no  advantage, 
in  our  ordinary  modern  life,  that  the  upper  arm 
should,  by  judiciously  and  ingeniously  planned  ex- 
ercise, grow  to  be  an  inch  larger  than  it  was  a  year 
before,  and  to  the  ordinary  youth  the  duties  of  a 
gymnasium  are  irksome  to  the  last  degree. f  There 
is  no  evidence  that  athletes,  whose  bodies  are 
knobbed  with  unsightly  bunches  of  muscle,  are  any 
healthier  or  any  happier,  or  live  any  longer,  or  do 
any  more  good  in  the  world,  than  the  less  muscular 

*  These  remarks  apply  to  girls  as  well  as  to  boys.  Out-door  exer- 
cise of  an  agreeable  kind  is  as  necessary  for  the  health  of  one  as  of  the 
other.  The  hot-house  plant  is  never  strong,  and  the  tom-boy  grows  to 
be  the  most  healthy  and  vigorous  woman,  both  mentally  and  physically. 

f  It  is  not  to  be  understood  that  the  gymnasium  is  here  altogether 
condemned.  It  is  of  great  use  in  its  proper  sphere.  But  the  boy's  idea 
of  a  gymnasium  is  that  it  is  a  place  to  get  strong,  rather  than  healthy. 
The  surroundings  and  examples  are  such  as  to  encourage  straining  for 
effect,  lifting  heavy  weights  in  emulation,  and  the  like  acts,  which  may 
injure  a  boy  permanently.  When  gymnastic  exercises  are  performed 
under  a  competent  instructor,  with  proper  ends  in  view,  and  an  intelli- 
gent use  of  means  to  those  ends,  the  matter  is  altogether  different. 
But,  as  mentioned  in  the  text,  gymnastic  exercises,  excepting  for  the 
purpose  of  remedying  particular  defects,  training  special  muscles  for  a 
particular  purpose,  or  treating  actual  disease,  can  not  be  compared  in 
efficiency  with  out-door  sports. 


40 


ORGANS  OF  MOTION. 


person  who  confines  himself  to  simple  food,  who  in- 
sists upon  pure  air,  and  exercises  moderately  and  for 
his  own  pleasure  in  the  way  that  suits  him  best.* 

46.  Danger  of  Exhaustion. — But,  while  muscular 
exercise  is  necessary  to  continued  good  health,  it 
should  never  be  carried  to  the  point  of  exhaustion. 
This  is  dangerous,  not  only,  as  previously  indicated, 
because  the  nutrition  of  the  muscle  may  thus  be  in- 
terfered with,  but  because,  when  the  point  of  simple 
fatigue  is  passed,  and  exhaustion  supervenes,  the 
nervous  system  has  become  implicated  and  is  getting 
worn  out.  This  danger  will  be  better  understood 
when  that  part  of  our  bodies  is  described  hereafter. 
It  is  enough,  for  the  present,  to  remember  that  a 
person  is  not  harmed  by  being  tired,  but  that  it  ahvays 
Jiarms  one  to  be  exhausted. 

47.  Rest. — When  a  muscle  is  fatigued,  it  recov- 
ers very  fast  if  allowed  to  rest.  For  this  reason 
it  is  much  less  fatiguing  to  walk  an  hour  than  to 

*  The  muscular  strength  which  is  developed  by  gymnastic  training 
vanishes  when  the  training  ceases.  It  is  often  noticed  by  those  who 
practice  much  in  gymnasiums  that  constant  practice  is  necessary  to  re- 
tain what  increase  of  muscular  power  they  have  acquired.  There  seems 
to  be  a  normal  condition  of  the  muscular  system  in  each  individual,  to 
which  he  reverts  when  special  training  is  abandoned.  The  strong  men 
are  not  made  so  by  training  ;  they  are  born  with  a  tendency  to  a  pre- 
ponderance of  the  muscular  organs.  Marvelous  stories  are  told  of 
men  of  this  class.  It  is  said  of  Frederick  Augustus  of  Saxony,  King 
of  Poland  (1670-1733),  commonly  called  Augustus  the  Strong,  that  on 
one  occasion,  wishing  to  present  a  bouquet  to  a  lady,  and  seeing  nothing 
to  wrap  it  in,  he  took  a  silver  plate  from  the  table  and  folded  it  around 
the  stems  with  the  greatest  ease.  In  Dresden  is  exhibited  a  horseshoe, 
or  the  halves  of  it,  which  he  is  said  to  have  broken  with  one  hand. 
Similar  stories  are  told  of  Baron  Trenck  (1711-1747) ;  and  of  Milo,  of 
Crotona,  a  famous  athlete  (520  B.  c),  it  is  said  that  he  once  carried  a 
live  ox  on  his  shoulders  around  the  stadium,  then  killed  it  with  a  blow 
of  his  fist,  and  afterward  ate  the  whole  of  it  in  a  single  day. 


EXERCISE. 


41 


stand  still  an  hour.  In  the  former  case  the  muscles 
constantly  have  short  intervals  of  rest,  while  in  the 
latter  they  are  not  able  to  rest  at  all,  but  are  con- 
tinually in  a  state  of  contraction.  If  we  are  obliged 
to  stand  for  a  long  time,  therefore,  we  almost  instinct- 
ively change  our  position  frequently,  stand  on  one 
leg  and  then  on  the  other,  or  find  some  place  to 
lean  against,  in  order  to  give  the  muscles  the  rest 
they  need. 

Out-door  sports,  then,  are  more  healthful  than  gym- 
nastic exercises. 

Exercise  may  be  pushed  to  tlic  point  of  fatigue  with- 
out injury,  but  never  to  the  point  of  exhaustion. 


PART     III. 
ORGANS  OF  REPAIR. 


CHAPTER  I. 

FOOD. 

48.  Necessity  of  Food. — We  all  know  that,  as 
long  as  we  are  living  beings,  we  tend  constantly  to 
lose  weight.  In  our  excretions,  our  breath,  the  per- 
spiration, the  tears,  the  saliva,  we  lose  altogether 
several  pounds  a  day.  All  of  this  matter  is  so  much 
gone,  and  if  it  be  not  replaced  the  body  dies.  It 
can  not  be  too  clearly  impressed  upon  the  mind 
that  this  waste  or  loss  of  material  is  continuous 
and  inevitable.  The  processes  of  muscular  contrac- 
tion, of  secretion,  even  of  thought,  produce  sub- 
stances which  are  taken  up  by  the  blood  to  be  put 
out  of  the  body.  These  substances  are,  many  of 
them,  very  poisonous,  and  if  they  can  not  be  ex- 
pelled from  the  body  they  kill  it.*  They  are  not 
the  result  of  disease  ;  they  are  the  constant  product 
of  living  processes  in  a  healthy  body.     So  we  see 

*  Thus  a  substance  called  urea  is  excreted  from  the  body  through 
the  kidneys.  This  substance  is  very  poisonous,  and,  when  the  kidneys 
are  diseased  and  are  no  longer  able  to  discharge  all  of  it  from  the  body, 
it  accumulates  in  the  blood  and  finally  causes  death.  So  it  is  with  the 
bile  and  with  certain  matters  which  pass  away  in  the  breath  at  every 
respiration. 


FOOD. 


43 


that  there  must  be  a  continuous  expulsion  of  such 
matters,  and,  of  course,  what  each  part  of  the  body 
has  lost  by  such  a  process  must  be  replaced  with 
fresh  material. 

49.  Living  without  Food  impossible. — If  this  fact 
be  clearly  understood,  it  will  be  easy  to  see  that  the 
numerous  stories  about  persons  who  live  without 
eating  are  false.  If  such  persons  live,  their  hearts 
must  beat,  their  brains  must  think,  their  lungs  must 
move  in  breathing,  and  all  of  these  things  cause  in- 
evitably a  waste  of  material.  How  absurd,  then,  to 
gravely  talk  of  a  person  who  has  not  taken  any 
food  or  drink  for  six  months,  and  still  has  not  lost 
weight,  but  remains  plump  and  healthy  !  It  is  just 
as  absurd  as  it  would  be  to  say  that  such  or  such  a 
person  had  a  limb  amputated  day  after  day,  and  yet 
after  each  operation  weighed  as  much  as  before. 
These  cases  are  all  cheats,  for  if  there  is  waste  going 
on,  which  is  not  made  good,  the  body  must  decrease 
in  weight.  If  there  is  no  waste,  there  is  no  life,  no 
thought,  no  heart-beats,  no  respiration,  no  move- 
ment of  any  kind.  These  facts  of  the  generation  of 
force  by  food  and  of  constant  loss  and  gain  are  the 
chief  foundation-stones  of  all  correct  knowledge  of 
physiology,  and  can  not  be  too  firmly  fixed  in  the 
mind. 

50.  Classification  of  Food. — In  order  to  supply 
the  waste  in  our  bodies  we  need  a  great  variety  of 
food ;  and,  indeed,  the  procuring  and  preparing  of 
food  occupy  a  large  portion  of  the  lives  of  most  peo- 
ple. The  food  we  use  is  usually  classified  as  nitroge- 
nous and  non-nitrogcnoiis,  or  carbonaceous.  But,  besides 
these  two  great  divisions,  which  include  all  our  ani- 
mal and  vegetable  food,  there  are  some  substances 


44 


ORGAATS  OF  REPAIR. 


which  are  neither  animal  nor  vegetable,  and  yet  are 
quite  as  necessary  to  our  health  as  any  other  por- 
tion of  what  we  eat.  The  most  important  of  these 
are  water  and  salt. 

51.  Water. —  Water  is  present  in  a  greater  or  less 
quantity  in  every  part  of  the  body,  and,  as  it  is  rap- 
idly expelled,  it  has  to  be  frequently  supplied.  It 
constitutes  between  three  fourths  and  two  thirds  of 
the  entire  weight  of  the  body,  and  the  amount  re- 
quired for  an  adult  man  daily  is  about  three  pints, 
in  addition  to  that  which  forms  a  part  of  the  solid 
food.  The  quantity  used  varies  enormously,  accord- 
ing to  the  waste.  In  a  hot  day  in  summer  we  need 
much  more  than  in  cold  weather,  and  in  damp  days 
much  less  than  on  dry  ones. 

52.  Salt. — Salt,  also,  is  not  only  an  agreeable  con- 
diment, but  has  important  offices  to  perform  in  the 
body.  It  has  been  shown  by  experiments  on  ani- 
mals that,  if  they  are  entirely  deprived  of  salt,  they 
decline  very  much  in  vigor,  and  every  farmer  knows 
how  necessary  it  is  to  the  health  of  his  cattle  and 
sheep.* 

53.  Other  Inorganic  Matters. — There  are  other 

*  Boussingault,  a  French  chemist  (born  in  1802),  reported  in  1854 
some  experiments  he  had  made  in  regard  to  the  importance  of  salt  to 
cattle.  He  took  six  bullocks,  of  about  the  same  age  and  vigor,  and  fed 
them  alike,  excepting  that  to  three  of  them  he  gave  500  grains  of  salt 
every  day  and  to  the  others  none.  At  the  end  of  six  months  the  hides 
of  those  that  had  had  no  salt  were  rough  and  dull  in  color,  while  those 
of  the  others  were  shining  and  smooth.  At  the  end  of  a  year  the  salt- 
fed  bullocks  were  in  perfect  health,  while  the  others  were  dull  and 
stupid,  and  the  hair  upon  their  hides  was  rough  and  tangled,  with  bare 
patches  here  and  there. 

Wild  animals,  especially  of  the  grazing  kind,  like  deer  and  cattle, 
will  travel  long  distances  in  search  of  salt,  and  seem  to  be  as  fond  of 
it  as  children  are  of  sugar. 


FOOD.  45 

inorganic  matters  which  are  essential  to  the  growth 
and  nutrition  of  the  body,  but  which  are  naturally 
found  in  articles  of  food  and  are  not  taken  sepa- 
rately. Such  are  the  salts  of  lime,  soda,  potash,  and 
magnesia,  all  of  which  form  a  part  of  our  common 
fruits  and  vegetables.  The  most  important  of  these 
is  probably  the  lime  phosphate  which  forms  so  great 
a  part  of  the  bones.  The  husk  of  grain  contains  a 
certain  proportion  of  this  salt,  and  in  growing  chil- 
dren, in  Avhom  the  cartilaginous  portions  of  the 
bones  are  becoming  ossified,  wheaten  grits  or  Gra- 
ham bread  is  a  very  welcome  and  advantageous  ar- 
ticle of  diet.  It  has  been  affirmed  that  the  large  size 
of  the  inhabitants  of  Kentucky  is  due  to  the  fact  that 
they  live  in  a  limestone  region,  and  the  water  they 
use  is  strongly  impregnated  with  lime.  So  large  a 
proportion  of  lime  taken  into  the  body,  at  a  time 
when  the  bones  are  forming  and  growing  and  hard- 
ening, is  said  to  make  them  longer  and  stronger 
than  they  would  be  otherwise. 

54.  Non-nitrogenous  Foods.  —  The  non-nitroge- 
nous, or,  as  they  are  sometimes  called,  the  carbonaceous 
foods,  are  sugar,  starch,  and  fat.  These  substances 
are  all  composed  of  carbon,  hydrogen,  and  oxygen, 
in  varying  proportions,  the  sugar  and  starch  taken 
in  our  food  being  mostly  of  vegetable  origin,  while 
the  fat  may  be  either  animal  or  vegetable. 

55.  Starch. — Starch  forms  a  part  of  all  grains  and 
most  vegetables,  sago,  tapioca,  arrowroot,  etc.,  be- 
ing almost  pure  starch,  which  has  been  extracted 
from  the  plants  in  which  it  is  found.  Rice  contains 
about  85  per  cent  of  starch,  wheat  about  70  per 
cent,  and  the  potato  about  15  per  cent.  This  latter 
amount  seems  very  small,  but  most  of  the  remainder 


46  ORGANS  OF  REPAIR. 

of  the  ioo  parts  of  the  potato  consist  of  water,  and 
starch  really  forms  the  bulk  of  the  solid  matter. 

It  is  a  peculiarity  of  starch  that  it  is  very  easily 
converted  into  sugar.  This  is  actually  accomplished 
in  the  human  body,  during  the  processes  of  masti- 
cation and  digestion,  as  will  be  shown  hereafter. 

56.  Sugar. — Sugar  is  taken  in  our  food  in  various 
forms,  for  it  has  not  always  the  same  chemical  com- 
position. It  is  always  sweet,  and  is  always  easy  to 
recognize  as  sugar,  but  varies  in  its  proportions  of 
carbon,  hydrogen,  and  oxygen.  Thus  we  find  that 
cane-sugar,  milk-sugar,  and  grape-  or  honey-sugar 
(often  called  glucose  *),  all  differ  from  each  other. 
Sugar  is  taken  partly  as  an  addition  to  the  food  for 
the  sake  of  improving  its  flavor,  and  partly  as  a  nat- 
ural constituent  of  vegetables  and  particularly  of 
fruits,  some  of  which  contain  an  enormous  propor- 
tion of  it.  Figs,  for  example,  are  more  than  half 
sugar,  and  hardly  any  fruit  contains  less  than  10  per 
cent. 

57.  Fat. — Fat  is  found  in  almost  all  parts  of  the 
body,  and  particularly  just  underneath  the  skin, 
where  it  serves  to  give  rounded  outlines  to  the  form, 
and  also  undoubtedly  acts  as  an  elastic  cushion  to 
protect  the  parts  beneath  from  injury.  During  life, 
owing  to  the  warmth  of  the  body,  the  fat  is  fluid  and 
transparent ;  f  but  after  death,  as  the  body  cools,  it 

*  Glucose  is  now  produced  artificially  in  enormous  quantities  by  the 
use  of  sulphuric  acid  and  corn.  When  anything  containing  starch  is 
boiled  with  this  acid,  the  starch  is  converted  into  glucose,  which  is  the 
kind  of  sugar  found  in  fruits.  Cane-sugar  can  be  changed  into  glucose 
in  the  same  way,  and  as  a  matter  of  fact  it  is  changed  into  glucose  in 
the  act  of  digestion,  so  that  glucose  must  be  looked  upon  as  that  form 
of  sugar  that  it  is  natural  for  us  to  take  in  our  food. 

f  If  the  fingers  be  held  close  together  in  front  of  a  bright  light,  the 


FOOD. 


47 


becomes  solid.  The  fat  which  is  found  in  the  body 
is  not  all  taken  in  with  the  food,  but  a  certain  amount 
of  it  is  formed  in  the  body  itself,  in  a  manner  which 
is  not  yet  understood.  Certain  articles  of  diet  tend 
to  increase  the  amount  of  fat  in  the  body.  This  is 
notably  the  case  with  starch  and  sugar.  In  sugar- 
growing"  countries,  as  the  Southern  States,  it  is  a 
matter  of  common  observation  that  the  negroes  grow 
fat  and  sleek  during  the  sugar-season,  and  lose  their 
superabundant  flesh  when  the  season  is  over.  Arti- 
cles of  food  which  contain  much  starch  also  increase 
the  amount  of  fat  The  famous  Banting  system  of 
treating  corpulence  is  based  on  this  fact,  and  con- 
sists mainly  in  depriving  the  patient  of  starchy  vege- 
tables, grains,  and  sugar.* 

58.  Nitrogenous  Foods. — The  nitrogenous  portion 
of  our  food  is  also  both  animal  and  vegetable,  but 
chiefly  animal.  The  principal  substances  of  this  class 
are  fibrin,  albu'mcn,  and  caJsc'in,  They  all  contain  a 
considerable  amount  of  nitrogen,  in  addition  to 
carbon,  hydrogen,  and  oxygen,  and  are  generally 
called  by  plrysiologists  prd'teid  substances,  or  the 
proteids. 

Casein  is  found  in  large  proportion  in  milk,  from 
which  it  is  extracted  to  form  cheese,  and  the  two 

rosy  tinge  of  their  borders  shows  that  they  are  to  a  certain  extent  trans- 
lucent. The  ringers  of  a  corpse,  under  similar  conditions,  are  opaque. 
*  Mr.  Banting,  the  court  undertaker,  was  put  under  treatment  for 
corpulence  by  Mr.  William  Harvey,  a  London  surgeon.  He  was  al- 
lowed to  eat  any  meat  except  pork,  any  kind  of  fish  except  salmon  or 
eels,  any  vegetables  except  potatoes  or  rice,  any  kind  of  poultry  or 
game,  dry  toast,  fresh  fruit,  tea  without  milk  or  sugar,  and  to  drink 
claret,  sherry,  or  madeira  wine,  or  gin,  whisky,  or  brandy  without  sugar. 
When  he  began  this  diet  in  August,  1862,  he  weighed  two  hundred 
and  two  pounds,  and  a  year  after,  he  had  lost  forty-six  pounds,  and 
reduced  his  girth  twelve  and  a  quarter  inches. 


48  ORGANS  OF  REPAIR. 

others  arc  found  mostly  in  the  animal  fluids,  and  in 
muscular  fiber. 

There  are  also  substances  very  much  like  the 
animal  albumen  and  casein  which  are  found  in  vege- 
tables, but  they  present  slight  chemical  differences, 
although  they  probably  answer  nearly  the  same 
purpose  in  nutrition.  Peas  and  beans  contain  a  con- 
siderable quantity  of  the  vegetable  casein. 

59.  Necessity  of  Variety  of  Food. — It  is  neces- 
sary, for  the  preservation  of  health,  that  our  food 
should  contain  a  sufficient  amount  of  these  different 
kinds  of  matter.  We  must  have  water ;  we  must 
have  salt  and  the  lime  compounds  mentioned  above  ; 
we  must  have  starchy  substances  (much  the  same  to 
the  body  as  sugar)  and  fats,*  and  we  must  have  a 
certain  amount  of  nitrogenous  food.  If  one  of  these 
be  lacking,  the  body  soon  feels  it,  and,  although  the 
person  may  not  know  precisely  why  he  feels  bad, 
he  will  often  recover  from  his  temporary  disorder 
by  a  mere  change  of  diet.  The  lack  of  any  particu- 
lar ingredient  in  our  food  is  often  indicated  to  us  by 
a  longing  for  it.  We  feel  a  strong  desire  to  eat  par- 
ticular things  and  no  others,  and  such  a  desire  may 
generally  be  taken  as  a  safe  indication  that  the  body 
needs  them. 

60.  Paramount  Necessity  of  Water. — Of  all  arti- 
cles used  for  food  or  drink,  water,  in  some  form 
or  other,  is  the  most  indispensable.  Men  can  live 
much  longer  on  water  without  food  than  on  food 
without  water.  The  celebrated  French  physiolo- 
gist, Magendie,  found  that  dogs  lived  eight  or  ten 

*  This  is  said  of  a  healthy  person.  Excessive  production  of  fat,  as 
in  Mr.  Banting's  case,  is  to  be  regarded  as  a  diseased  condition,  and  so 
requires  special  diet. 


FOOD. 


49 


days  longer,  when  supplied  with  water  alone,  than 
when  they  were  deprived  of  both  food  and  water. 
The  pangs  of  thirst  have  been  felt  in  a  slight  de- 
gree by  almost  every  one,  and  it  is  the  experience 
of  those  who  have  suffered  from  deprivation  of 
food  and  water,  in  deserts  and  shipwrecks,  that  the 
tortures  of  thirst  are  much  harder  to  bear  than 
those  of  hunger. 

61.  Daily  Amount  of  Food. — It  has  been  found 
by  Dr.  Dalton,  by  experiments  upon  himself,  that 
an  adult  requires  food  in  about  the  following  pro- 
portions : 

Meat 16  ounces. 

Bread 19       " 

Butter,  or  fat i\     " 

Water 52       " 

or  about  two  pounds  and  a  half  of  solid  food  and 
about  three  pints  of  liquid  food  daily.  This  is 
about  the  least  amount  which  will  keep  him  in 
good  health. 

62.  Cooking. — Man  does  not  take  his  food  in 
the  natural  state,  like  other  animals,  but  prepares 
it  by  cooking.  This  process  is  of  advantage  in  two 
ways :  it  softens  the  hard  parts  of  the  food,  such 
as  beans,  potatoes,  and  the  various  grains,  and  the 
fibrous  tissue  of  meat ;  and  it  also  develops  a  pleas- 
ant flavor  by  the  action  of  heat,  which  excites  the 
flow  of  the  fluids  of  the  mouth  and  stomach,  and 
thus  aids  digestion. 


CHAPTER   II. 

MASTICATION. — SWALLOWING. 

63.  The  Digestive  Apparatus. — The  food  we 
eat  is  mostly  insoluble,  and  in  an  unfit  condition 
to  be  used  for  the  nourishment  of  the  body.  Even 
so  nutritious  a  substance  as  albumen  can  not  be 
used  without  undergoing  some  change,  and  if  pure 
fluid  albumen  be  injected  directly  into  the  blood,  it 
will  be  thrown  out  of  the  body  by  the  kidneys  un- 
altered. To  prepare  the  various  foods  for  use  in 
the  body,  we  are  provided  with  a  complicated  series 
of  organs,  called  the  digestive  apparatus,  in  which 
the  food  is  ground  fine  and  mingled  with  various 
juices  until  it  is  reduced  to  a  fluid  mass,  which  can 
be  taken  up  by  the  blood  and  carried  to  all  parts 
of  the  body  in  a  condition  fit  for  their  nutrition. 

64.  Processes  to  which  Food  is  subjected  in 
the  Body. — The  process  of  preparing  food  for  our 
nourishment  may  be  conveniently  divided  into 
five  stages.  The  first  of  these  is  mastication,  which 
takes  place  in  the  mouth,  and  is  a  voluntary  act. 
The  second  is  siv allowing,  or  the  act  of  passing  food 
on  from  the  mouth  to  the  stomach,  the  beginning 
of  this  act  being  voluntary,  and  the  greater  part  of 
it  involuntary.  The  third  is  stomach  digestion,  which 
is  involuntary  ;  the  fourth,  intestinal  digestion,  which 


MASTIC  A  TION.—S  WALLO  WING. 


51 


,sE  tmes  A/re 
ft*  \  giooo  vessels      °Ss 

4u 


Fig.  19. — Front  view  of  the  organs  in  their  natural  relations.  The  heart  is 
partly  covered  by  the  lungs,  but  its  true  outline  is  indicated  by  a  dotted 
line.  Only  ten  ribs  are  shown  on  each  side,  the  eleventh  and  twelfth 
(the  floating  ribs)  being  too  short  to  be  included  in  the  section. 


52  ORGANS  OF  REPAIR. 

is  involuntary  ;  and  the  fifth  is  the  process  of  ab- 
sorption, which  is  also  a  process  of  selection,  by 
which  certain  portions  of  the  prepared  mass  are 
taken  up  into  the  circulation  for  food,  and  the  rest 
left  in  the  intestines  as  waste  material ;  this  whole 
process  is  also  beyond  the  control  of  our  will ;  all 
waste  matters  are  then  expelled  from  the  body. 

65.  Only  One  Voluntary  Process. — All  of  these 
processes  must  be  properly  conducted,  in  order  to 
maintain  the  body  in  a  healthy  condition.  They 
are  all  important,  and,  if  one  be  neglected  or  carried 
on  in  a  disordered  and  unnatural  manner,  the  others 
will  all  be  affected,  by  reason  of  their  close  connec- 
tion with  and  dependence  on  each  other.  Only  one 
of  them  is  directly  under  the  control  of  the  will,  and 
every  one  can  do  more  toward  preventing  dyspep- 
sia and  other  disorders  of  the  digestive  organs,  by 
paying  some  attention  to  the  proper  and  complete 
mastication  of  his  food  than  in  almost  any  other 
way.  If  we  examine  the  montJi,  with  reference  to 
its  uses  in  mastication,  we  find  it  prepared  to  per- 
form three  great  and  important  functions. 

66.  Use  of  the  Taste  and  Smell. — In  the  first 
place,  it  is  provided  with  an  organ  of  taste,  to  assist 
us  in  selecting  our  food.  In  this  it  is  aided  by  the 
proximity  of  the  nose,  so  that  we  have  the  addi- 
tional advantage  of  the  sense  of  smell.  And  the 
nose  is  not  only  so  situated  as  to  aid  us  in  judging 
of  food  before  it  enters  the  mouth,  but  it  is  con- 
nected with  the  throat  behind,  so  that  odors  are 
detected  from  substances  already  in  the  mouth. 

67.  The  Teeth. — In  the  second  place,  the  mouth 
is  provided  with  organs  for  grinding  and  crushing 
the  hard  parts  of  the  food,  and  reducing  them  to  a 


MASTIC  A  TION.—S  WALLO  WING. 


53 


Fig.  20. — Section  of  a 
tooth.  The  black 
portion  is  the  cav- 
ity occupied  by  the 
nerve  and  blood- 
vessels. 


soft  mass,  fit  to  be  acted  upon  by  the  fluids  in  the 
stomach  and  intestines.  The  organs  directly  of 
use  in  this  operation  are  the  teeth  (Fig.  20),  but 
essential  aid  is  afforded  by  the  mus- 
cles of  the  checks  and  the  tongue. 
The  rows  of  teeth  are  narrow,  and, 
except  for  the  action  of  these  mus- 
cles, the  food  could  not  be  kept  be- 
tween them.  Indeed,  it  has  been 
found  that  in  cases  of  paralysis, 
when  the  muscles  of  the  cheek  are 
unable  to  contract,  while  the  tongue 
still  retains  its  power,  the  food  gets 
pushed  out  between  the  cheek  and 
the  teeth,  and  accumulates  there. 
The  lower  jaw  is  moved  by  some 
of  the  most  powerfully  acting  mus- 
cles in  the  body.  The  chief  one  of  all  is  the  mas'- 
scter,  which  is  attached  above  to  the  ridge  of  bone 
running  backward  from  the  lower  border  of  the 
eye  toward  the  ear,  and  below  to  the  horizontal 
portion  of  the  jaw.  The  muscle  is  nearly  square  in 
shape,  and,  as  is  easily  seen,  acts  at  a  great  mechan- 
ical advantage.  As  a  matter  of  interest  connected 
with  this  muscle,  it  may  be  stated  that  it  is  the  mus- 
cle generally  referred  to  for  proof  that  muscular 
contraction  is  accompanied  by  a  sound.  If  the 
lower  jaw  be  firmly  closed,  and  the  teeth  powerfully 
pressed  together  so  that  the  muscles  of  mastication 
are  strongly  contracted,  a  low,  rumbling  sound  will 
be  heard,  which  can  not  be  explained  in  any  other 
way  than  as  caused  by  the  muscular  contraction. 

68.  The  Saliva. — In  the  third  place,  the  food, 
while  undergoing  mastication,  is  mixed  with  cer- 


54 


ORGANS  OF  REPAIR. 


tain  fluids,  called  collectively  the  saliva.  They  are 
the  product  of  three  sets  of  glands,  each  of  which 
is  double — i.  e.,  there  are  three  glands  on  each  side 
of  the  mouth  (Fig.  21),  and  the  secretion  of  each 


Fig.  21. — The  salivary  glands  of  the  right  side. 

pair  is  peculiar  to  itself.  The  largest  of  these  are 
the  par vt 'id  glands,  which  are  situated  just  in  front 
of  the  lower  border  of  the  ears,  and  are  the  glands 
which  become  swollen  and  cause  the  distortion  of 
the  face  in  the  disease  known  as  the  mumps.  The 
fluid  secreted  by  these  glands  is  very  thin  and 
watery,  and  constitutes  the  greater  part  of  the  sa- 


MASTIC  A  TION.—S  WALLO  WING. 


55 


liva.  The  other  glands  are  situated  just  inside  the 
lower  border  of  the  jaw  and  beneath  the  tongue. 
Their  secretion  is  much  thicker  and  more  glutinous 
than  that  of  the  parotid  glands.  Besides  these 
fluids,  there  is  a  small  amount  secreted  by  the 
mucous  membrane  lining  the  mouth,  and  all  these 
mingled  fluids  constitute  the  saliva. 

The  saliva  is  secreted  to  some  extent  at  all 
times,  and  keeps  the  lining  membrane  of  the  mouth 
moist  and  soft,  but  it  is  a  familiar  fact  that  its 
amount  is  greatly  increased  at  certain  times.  Thus, 
we  say,  at  the  sight,  or  even  sometimes  at  the  sug- 
gestion, of  an  appetizing  meal,  the  "  mouth  waters."  * 
The  fact  of  its  excessive  secretion  at  such  times 
shows  that  it  has  a  part  to  perform  in  the  process 
of  mastication  and  digestion. 

69.  Properties  and  Use  of  the  Saliva. — Experi- 
ments have  shown  that  saliva  possesses  the  property 
of  converting  starch  into  sugar ;  but,  as  this  is  also 
done  by  the  digestive  fluids,  it  is  not  considered  to 
be  a  very  important  function,  and  the  chief  use  of 
the  saliva  undoubtedly  is,  to  make  the  processes  of 
mastication  and  swallowing  of  food  easier.  If  food 
were  taken  dry,  and  there  were  no  means  at  hand 
of  moistening  it,  mastication  would  be  very  difficult 
and  tiresome,  and  swallowing  almost  impossible. 
Bernard  f  found,  by  experiments  upon  a  horse,  that 

*  In  physiological  lectures  before  medical  students,  it  is  not  uncom- 
mon to  illustrate  this  fact  in  a  curious  way.  A  slender  tube  is  intro- 
duced into  the  opening  by  which  the  parotid  saliva  is  discharged  into 
the  mouth,  and,  according  to  the  condition  of  the  person  operated  on, 
there  will  either  be  no  flow  of  saliva  or  it  will  come  out  drop  by  drop. 
But  now  let  food  be  brought  in,  and  the  moment  it  is  seen  the  saliva 
begins  to  run  from  the  tube  in  a  plentiful  stream. 

f  Claude  Bernard,  a  famous  French  physiologist  (1813-1S7S).     He 


5  6  ORGANS  OF  REPAIR. 

when  an  operation  had  been  performed,  which  pre- 
vented the  parotid  saliva  from  entering  the  mouth, 
the  animal  could  masticate  and  swallow  (the  latter 
process  being  accomplished  with  great  difficulty) 
only  three  quarters  as  much  oats  in  twenty-five 
minutes  as  he  had  previously  eaten  in  nine.  It  is 
probable  that  the  parotid  saliva,  which  is  almost 
like  water,  assists  mainly  in  the  mastication  of  the 
food ;  while  the  other  secretions,  which  are  thicker 
and  more  slippery,  coat  the  outside  of  the  mass,  and 
render  it  easier  to  swallow. 

The  total  amount  of  saliva  secreted  by  a  healthy 
adult  in  twenty-four  hours  has  been  calculated,  after 
numerous  experiments,  to  be  nearly  three  pounds. 

Note. — It  is  important  for  the  health  of  the  individual  that  the 
teeth  should  be  kept  in  good  condition,  in  order  that  mastication  may 
be  thorough  and  complete.  Particles  of  food  which  stick  between  the 
teeth,  if  they  are  allowed  to  remain,  putrefy  and  impart  an  offensive 
odor  to  the  breath.  The  acids  which  are  developed  during  the  putre- 
factiqn  of  such  matters  are  also  injurious  to  the  teeth  and  tend  to  hasten 
their  decay.  There  are  also  certain  substances  deposited  from  the 
saliva  around  the  necks  of  the  teeth,  called  "tartar."  If  this  is  not 
removed,  the  gums  are  bruised  against  it,  and  finally  recede  from  the 
teeth,  leaving  a  part  of  the  fang  bare,  and  thus  exposing  to  all  sorts  of 
injurious  influences  a  part  of  the  tooth  which  was  never  intended  to 
be  so  exposed. 

The  teeth  should  therefore  be  frequently  cleaned,  at  least  twice  a 
day,  with  water  and  a  soft  brush  (a  stiff  brush  injures  the  gums),  tooth- 
picks being  used  when  necessary.  Avoid  fancy  tooth-powders  and 
washes,  for  they  often  contain  injurious  acids  or  gritty  substances.  To 
polish  the  teeth,  use  powdered  orris-root  and  chalk,  which  can  be 
bought  of  any  druggist.  Never  crack  nuts  with  the  teeth,  and,  on  the 
slightest  appearance  of  decay,  consult  a  good  dentist. 

was  Professor  of  Physiology  in  the  College  of  France  from  1855  until 
his  death.  Especially  distinguished  for  his  discovery  of  the  formation 
of  sugar  in  the  liver,  and  for  his  researches  on  the  functions  of  the  sym- 
pathetic nervous  system.     (See  later.) 


CHAPTER   III. 

STOMACH-DIGESTION. 

70.  The  Alimentary  Canal. — The  food,  which  is 
now  ready  to  be  operated  upon  by  the  digestive 
fluids,  passes  beyond  the  control  of  the  person  who 
swallows,  and  begins  its  travels  in  the  long  tube, 
called  the  aliment' ary  canal  (Fig.  22).  This  canal 
begins  at  the  mouth  and  ends  with  the  large  intes- 
tine, and  is  nearly  thirty  feet  in  length.  It  does 
not  properly  assume  the  form  of  a  tube  until  the 
beginning  of  the  cesopli'agns,  or  gullet,  and  at  one 
point,  namely,  at  the  lower  extremity  of  the  oesoph- 
agus, there  is  a  considerable  enlargement,  which 
has  the  appearance  of  a  bag  or  pouch,  and  is  called 
the  stomach.  To  understand  the  working  of  the 
alimentary  canal,  it  is  necessary  to  know  something 
of  its  anatomy. 

The  two  most  important  tissues  in  its  structure 
are  the  mucous  membrane  which  lines  it  through- 
out, and  the  muscles  which  surround  it,  and  are  im- 
bedded in  its  walls. 

71.  Mucous  Membrane. — Mucous  membrane  (Fig. 
23)  is  the  skin  which  lines  the  interior  canals  of  the 
body.  While  the  outside  of  the  body  is  covered 
by  a  smooth,  white,  tough  skin,  we  see  that,  at  the 
openings  leading  to  its  interior,  such  as  the  mouth, 


58 


ORGANS  OF  REPAIR. 


nose,  etc.,  the  character  of  this  covering"  suddenly 
changes,  and  it  becomes  a  reddish  or  pinkish  mem- 


OESOPHAGUS- 


Fig.  22. — The  alimentary  canal. 

brane  very  soft  and  delicate  in  texture,  and  con- 
tinually moistened  by  its  secretions.  This  is  called 
mucous  membrane,  and  in  one  form  or  another  it 
lines  all  those  internal  parts  of  the  body,  which 
communicate  with  the  external  air. 

It  is  made  up  mainly  of  fibrous  tissue,  consisting 
of  fine  threads,  interlacing  with  each  other  in  every 
direction  and  densely  woven.      Its  surface  is  cov- 


STOMACH-DIGESTION. 


59 


Fig.  23. — Structure  of  mucous  membrane 
illustrated.  At  one  side  is  a  detached 
portion  of  a  tube,  or  follicle,  enlarged  so 
as  to  show  the  epithelium  more  clearly. 


ered  with  minute  cells,  called  epithe'lial  cells*  At 
various  points  on  the  membrane  are  minute  tubes 
or  cavities,  less  than 
y^-q  of  an  inch  in  diam- 
eter,of  different  shapes 
in  different  places,  and 
in  some  situations  so 
numerous  that  they  lie 
almost  in  contact  with 
each  other.  These  mi- 
nute tubes  are  closed 
at  the  bottom,  but 
open  on  the  surface  of  the  membrane.  Small  as 
they  are,  they  are  lined  from  top  to  bottom  with 
epithelial  cells,  which  really  carry  on  the  work  of 
secretion.  All  around,  among,  and  underneath 
these  tubes  are  small  blood-vessels,  which  nourish 
the  membrane,  and  from  which  the  little  epithelial 
cells  separate  the  materials  which  form  the  mucus. 
72.  Muscles  of  the  Alimentary  Canal. — The  mus- 
cles which  form  a  considerable  part  of  the  walls  of 
the  alimentary  canal  are  of  the  involuntary  or  non- 
striated  kind.  The  fibers  run  in  various  directions, 
some  of  them  surrounding  the  oesophagus  and  the 

*  All  free  surfaces  of  the  body,  whether  inside  or  outside,  are  cov- 
ered with  cells.  In  the  interior  of  the  body,  the  alimentary  canal,  the 
lungs  etc.,  these  cells  are  soft,  and,  so  to  speak,  plump,  and  are  called 
epithelial  cells,  or  a  mass  of  them  taken  together  is  called  epithelium. 
On  the  external  surface  of  the  body  they  are  dry,  flat,  hard,  and  horny, 
and  are  called  epider  mal  cells,  or,  in  a  mass,  the  epidermis.  In  both 
situations  they  are  being  constantly  shed  and  renewed.  The  fresh 
ones  are  continually  forming  underneath,  and,  as  they  grow,  take  the 
place  of  the  old  ones  on  the  surface,  which  are  being  constantly  rubbed 
off  in  one  way  or  another.  All  the  secretions  of  mucous  membranes 
contain  these  epithelial  cells,  and  the  slightest  scraping  of  the  skin  dis- 
lodges epidermal  cells. 


60  ORGANS  OF  REPAIR. 

intestines  in  a  circle,  so  that  when  they  contract 
they  make  the  canal  smaller ;  while  others  run 
lengthwise,  and  their  contraction  shortens  the  ca- 
nal. When  these  two  kinds  of  fibers,  the  circular 
and  the  longitudinal,  contract  together,  they  propel 
forward  anything  that  comes  within  their  grasp. 

73.  Serous  Membrane. — Besides  these  parts  of 
their  structure,  the  stomach  and  intestines  are  cov- 
ered on  the  outside  by  what  is  called  a  serous  mem- 
brane, which  is  found  lining  all  cavities  inside  the 
body  that  do  not  communicate  with  the  air,  ex- 
cepting the  joints.  This  kind  of  membrane  is  trans- 
parent, exceedingly  fine  and  soft,  and  smooth  like 
satin,  and  is  constantly  moistened  with  a  slight 
amount  of  fluid.  The  use  of  serous  membrane  is 
to  allow  organs  to  move  freely  upon  each  other 
without  friction.  If  it  were  not  for  some  provision 
of  this  sort,  the  movements  of  the  stomach  and  in- 
testines during  digestion  would  be  painful,  or  at 
least  disagreeable,  while,  as  things  now  are,  we  are 
entirely  unconscious  of  any  movement  at  all. 

74.  Swallowing. — After  mastication  is  completed 
the  tongue  passes  the  mass  of  food  backward  into 
the  phar'ynx  (or  throat),  whence  it  goes  on  into  the 
oesophagus.  The  oesophagus  (Fig.  24)  is  about  nine 
inches  long,  and  extends  from  the  throat  to  the 
stomach,  not  just  behind  the  breastbone,  as  many 
suppose,  but  just  in  front  of  the  spine.  The  mus- 
cles of  the  upper  portion  are  of  the  striated  variety, 
but,  nevertheless,  their  contraction  is  not  voluntary. 
When  anything  has  once  passed  to  the  back  of  the 
throat,  it  will  be  swallowed  and  sent  into  the  stom- 
ach, in  spite  of  our  will. 

75.  The  Stomach. — The    stomach  varies  in  size 


STOMACH-DIGESTION. 


61 


in   different  persons,  but  on  the  average  will  con- 
tain about   three  pints   of  fluid   in   the    adult.     Its 


Fig.  24. — Vertical  section  of  the  head  and  neck.  At  the  base  of  the  tongue 
is  seen  the  epiglottis,  and  below  this  the  larynx.  Between  the  larynx 
and  the  bodies  of  the  vertebrae  lies  the  cesophagus. 

shape  has  often  been  compared  to  that  of  the  air- 
bag  of  a  bag-pipe,  which  it  much  resembles  (Fig. 
25).  It  has  two  openings,  one  at  the  lower  extrem- 
ity of  the  cesophagus,  where  food  enters,  and  the 
other  at  the  point  where  food  passes  out  and  the 
small  intestine  begins.  These  openings  are  both  in 
4 


62 


ORGANS  OF  REPAIR. 


the  upper  border  of  the  organ,  and  only  a  short  dis- 
tance apart,  the  pylo'rus,  or  exit,  being  at  the  right 


Fig.  25. — Outside  of  the  stomach,  front  view,  showing  the  muscular  coat. 


extremity,  and  the  car'diac  opening  near  the  mid- 
dle."* The  stomach  extends  toward  the  left  for 
about  three  inches  beyond  the  cardiac  orifice,  and 
is  larger  in  this  part  than  in  any  other.  This  por- 
tion is  called  the  great  pouch  of  the  organ  (Fig.  26). 
Each  orifice  is  guarded  by  a  powerful  muscle, 
surrounding  it  in  a  circular  form,  which  can  con- 
tract so  tightly  as  to  prevent  the  passage  even  of  a 
fluid.  As  a  rule,  these  muscles  prevent  the  passage 
of  any  substance  backward  through  them,  in  oppo- 
sition to  the  natural  course  of  the  food. 

*  Pylorus,  a.  Greek  word  meaning  the  gate-keeper  ;  cardiac,  from  a 
Greek  word  meaning  the  heart,  because  it  is  very  near  that  organ. 


STOMACH-DIGESTION.  63 

76.  Stomach-Digestion.  —  It  was  formerly  sup- 
posed   that   the   whole    process   of    digestion   was 


Fig.  26. — Inside  of  the  stomach,  front  view,  showing  the  folds  (or  rugae)  of 
the  mucous  membrane. 


performed  in  the  stomach,  but  this  is  now  known 
not  to  be  the  case.  The  nitrogenous  portions  of 
the  food  are  the  only  ones  that  are  digested  in  the 
stomach.  The  oily  and  fatty,  as  well  as  the  starchy, 
portions  are  digested  in  the  small  intestines.  Fluids 
are  very  rapidly  absorbed  by  the  stomach. 

77.  Dr.  Beaumont  and  St.  Martin. — There  are  so 
many  difficulties  connected  with  the  investigation  of 


64  ORGANS  OF  REPAIR. 

the  subject  of  digestion,  that  very  little  was  really 
known  about  it  until  the  year  1833,  when  a  small 
book  was  published  by  Dr.  Beaumont,  of  the  United 
States  Army,  giving  physiologists  their  first  precise 
knowledge  of  what  takes  place  in  the  human  stom- 
ach. His  observations  were  so  well  taken,  that 
very  little  has  been  added  since  to  what  he  dis- 
covered upon  the  particular  subject  of  stomach 
digestion. 

In  the  year  1822,  Alexis  St.  Martin,  a  stout  young 
French  Canadian,  in  the  employ  of  a  fur-trading 
company,  and  about  eighteen  years  of  age,  received 
a  severe  wound  in  the  left  side  from  the  accidental 
discharge  of  a  shot-gun  at  a  distance  of  about  three 
feet.  He  was  attended  by  Dr.  Beaumont,  and, 
although  his  recovery  was  slow,  his  health  was 
finally  completely  re-established,  and  he  was  still 
living  in  Vermont,  the  father  of  a  numerous  family, 
at  a  very  recent  date.  In  the  situation  of  the 
wound,  however,  was  left  an  opening  into  the 
stomach,  about  four  fifths  of  an  inch  in  diameter, 
closed  by  a  flap  or  valve  of  mucous  membrane  on 
the  inside.  This  valve  could  be  pushed  inward,  but 
not  outward ;  and  thus,  although  the  operation  of 
digestion  was  not  at  all  interfered  with,  the  interior 
of  the  stomach  could  be  thoroughly  examined,  and 
experiments  performed  with  the  greatest  facility 
and  accuracy.  Dr.  Beaumont  kept  the  young  man 
in  his  employ  for  several  years,  and  made  hundreds 
of  observations  upon  him.  These  were  published 
in  his  little  book,  and  made  both  him  and  St.  Martin 
immediately  famous. 

As  Dr.  Beaumont  was  the  first,  and  for  many 
years  the  only,  person  who  ever  saw  the  interior  of 


S  TO  MA  CH-DIGES  TION.  65 

the  stomach  in  a  living  man,  much  of  the  following 
description  will  be  taken  from  his  volume. 

78.  Interior  of  the  Stomach. — "  The  interior  coat 
of  the  stomach,"  he  says,  "  in  its  natural  and  healthy 
state,  is  of  a  light  or  pale-pink  color,  varying  in  its 
hues  according  to  its  full  or  empty  state.  It  is  of 
a  soft  or  velvet-like  appearance,  and  is  constantly 
covered  with  a  very  thin,  transparent,  viscid  mucus, 
lining  the  whole  interior  of  the  organ." 

79.  The  Gastric  Juice. — The  changes  which  the 
food  undergoes  in  the  stomach  are  due  to  the  action 
of  the  gastric  juice,  the  appearance  of  which,  with 
the  manner  of  its  secretion,  is  thus  described : 

"  By  applying  aliments  or  other  irritants  to  the 
internal  coat  of  the  stomach,  and  observing  the 
effect  through  a  magnifying-glass,  innumerable  mi- 
nute lucid  points  can  be  seen  arising  from  the 
mucous  membrane,  and  protruding  through  the 
mucous  coat ;  from  which  distils  a  pure,  limpid, 
colorless,  slightly  viscid  fluid.  This  fluid  is  inva- 
riably distinctly  acid." 

"  The  fluid  so  discharged  is  absorbed  by  the 
aliment  in  contact,  or  collects  in  small  drops  and 
trickles  down  the  sides  of  the  stomach  to  the  more 
depending  parts,  and  there  mingles  with  the  food 
or  whatever  else  may  be  contained  in  the  gastric 
cavity." 

"  The  gastric  juice  never  appears  to  be  accumu- 
lated in  the  cavity  of  the  stomach  while  fasting. 
When  aliment  is  received,  the  juice  is  given  out  in 
exact  proportion  to  its  requirements  for  solution, 
except  when  more  food  has  been  taken  than  is  necessary 
for  the  wants  of  the  system." 

80.  Composition  and  Amount  of  Gastric  Juice. — 


66  ORGANS  OF  REPAIR. 

The  gastric  juice  contains  two  important  constitu- 
ents, viz.,  hydrochloric  acid  and  pepsin.  If  it  be 
deprived  of  these,  it  will  no  longer  exhibit  its  pe- 
culiar properties ;  while,  if  it  retains  them,  as  Dr. 
Beaumont  first  showed,  it  will  digest  food  in  a  glass 
tube,  outside  the  body,  provided  the  tube  and  its 
contents  be  kept  at  a  temperature  of  ioo°  Fahr., 
which  is  about  the  ordinary  temperature  inside  the 
stomach. 

The  average  amount  of  gastric  juice  secreted 
daily  by  an  adult  human  being  has  been  estimated 
at  a  little  less  than  fourteen  pounds,  or  about  a  gallon 
and  a  half. 

81.  Movements  of  the  Stomach. —  But,  besides 
the  action  of  the  gastric  juice  in  stomach-digestion, 
a  very  important  office  is  performed  by  the  muscles 
which  form  a  large  part  of  the  walls  of  the  organ. 
During  digestion,  these  muscles  are  continually 
contracting  in  a  slow,  regular  order,  producing 
movements  of  the  contents  of  the  stomach  in  a 
very  peculiar  manner,  which,  in  health,  never  varies. 
Dr.  Beaumont  says  that  the  ordinary  course  and 
direction  of  the  revolutions  of  the  food  are  first, 
after  passing  out  of  the  oesophagus  into  the  stom- 
ach, from  right  to  left,  thence  down  along  the  great 
curvature,  from  left  to  right,  to  the  pylorus,  whence 
it  returns  again  along  the  upper  border  of  the  or- 
gan to  the  left  extremity  of  it.  Each  of  these  jour- 
neys of  the  food  around  the  organ  occupies  from 
one  to  three  minutes,  and  they  serve  to  mingle  the 
gastric  juice  more  thoroughly  with  the  food.  As 
soon  as  the  process  of  digestion  is  gone  so  far  as  to 
bring  portions  of  the  food  into  a  condition  for  ab- 
sorption, it  is  found  that  every  time  the  contents  of 


S  TO  MA  CH-DIGES  TION.  6  7 

the  stomach  pass  the  pylorus  the  mass  becomes  di- 
minished in  amount,  showing  that  a  portion  has 
been  squeezed  or  pressed  through  the  opening  into 
the  intestine. 

"  These  peculiar  motions  and  contractions  con- 
tinue until  the  stomach  is  perfectly  empty,  and  not 
a  particle  of  food  remains.  Then  all  becomes  quiet 
again." 

Thus  that  part  of  the  digestion  of  food  which  is 
carried  on  in  the  stomach  is  accomplished  by  the 
action  of  the  gastric  juice,  and  the  changes  pro- 
duced by  it  are  assisted,  and  the  prepared  food  is 
passed  out  of  the  stomach,  by  the  constant  contrac- 
tions and  churning  motions  of  the  organ  just  de- 
scribed. 

This,  then,  is  the  ordinary  healthy  process  of 
stomach-digestion,  when  not  in  any  way  hindered 
or  interfered  with.  Let  us  see  what  changes  take 
place  in  the  appearance  of  the  stomach  and  in  its 
functions  when  it  is  injuriously  affected. 

82.  Appearance  of  the  Stomach  during  Indiges- 
tion. — "  In  a  feverish  condition,  from  whatever 
cause — obstructed  perspiration,  undue  excitement 
by  stimulating  liquors,  overloading  the  stomach 
with  food — fear,  anger,  or  whatever  depresses  or 
disturbs  the  nervous  system,"  the  lining  of  the  stom- 
ach "  becomes  somewhat  red  and  dry,  at  other  times 
pale  and  moist,  and  loses  its  smooth  and  healthy 
appearance  ;  the  secretions  become  vitiated,  greatly 
diminished,  or  entirely  suppressed." 

11  There  are  sometimes  found,  on  the  internal 
coat  of  the  stomach,  eruptions  or  deep-red  pimples. 
These  are  at  first  sharp-pointed  and  red,  but  fre- 
quently become  filled  with  white  purulent  matter; 


68  ORGANS  OF  REPAIR. 

at  other  times,  red  patches,  from  half  an  inch  to  an 
inch  and  a  half  in  circumference,  are  found  on  the 
internal  coat.  These  appear  to  be  the  result  of  con- 
gestion in  the  minute  blood-vessels  of  the  stomach." 

"  These  diseased  appearances,  when  very  slight, 
do  not  always  affect  essentially  the  gastric  appa- 
ratus. When  considerable,  and  particularly  when 
there  are  corresponding  symptoms  of  disease,  as 
dryness  of  the  mouth,  thirst,  furred  tongue,  etc., 
no  gastric  juice  can  be  extracted.  Drinks  received 
are  immediately  absorbed  or  otherwise  disposed 
of ;  none  remaining  in  the  stomach  ten  minutes  after 
being  swallowed.  Food,  taken  in  this  condition  of  the 
stomach,  remains  undigested  for  twenty-four  or  forty- 
eight  hours  or  more." 

"  Whenever  this  morbid  condition  of  the  stom- 
ach occurs,  with  the  usual  accompanying  symptoms 
of  disease,  there  is  generally  a  corresponding  ap- 
pearance of  the  tongue.  When  a  healthy  state  of 
the  stomach  is  restored,  the  tongue  invariably  be- 
comes clean." 

These  are  the  observations  of  one  who  saw  what 
he  describes,  and  took  careful  notes  of  what  he 
saw. 

83.  Time  required  for  Stomach-Digestion. — The 
time  required  for  digestion  in  the  stomach  varies 
very  much  according  to  the  character  of  the  food. 
Dr.  Beaumont  found  that  the  time  of  stomach-di- 
gestion in  St.  Martin  varied  from  one  hour  to  about 
five  and  a  half.  Among  meats,  the  soonest  digested 
was  boiled  pig's  feet,  which  took  an  hour,  and  the 
longest  time  was  taken  for  roast  pork,  viz.,  five 
hours  and  a  quarter  ;  among  vegetables,  rice  is  di- 
gested in  an  hour,  while  boiled  cabbage  requires 


STOMACH-DIGESTION.  69 

four.     The  average  time  required  for  an  ordinary- 
meal  is  probably  about  three  hours. 

84.  Advantage  of  Thorough  Mastication. — Dr. 
Beaumont  found  that,  when  a  piece  of  meat  or  other 
food  is  attacked  by  the  gastric  juice,  it  is  slowlv 
dissolved  from  the  outside.  The  juice  is  not  soaked 
up  and  does  not  penetrate  the  interior  of  the  mass, 
but  gradually  softens  the  exterior  of  it ;  and,  as 
the  outside  portion  becomes  friable  and  dissolves, 
the  piece  grows  smaller  and  smaller,  the  gastric 
juice  in  this  way  advancing  little  by  little,  until  the 
whole  mass  is  liquefied.  From  this  it  is  evident 
that  it  will  take  longer  to  digest  a  large  piece  of 
meat  than  to  digest  the  same  amount  after  it  has 
been  divided  into  small  pieces  ;  for  this  reason  it  is 
important  to  masticate  the  food  thoroughly  before 
sending  it  into  the  stomach. 

85.  Eating  too  little. — It  is  evident  that  it  will 
not  do  to  take  too  little  food.  Enough  must  be 
eaten  to  supply  the  needs  of  the  system,  and  it 
must  be  of  such  a  quality  that  it  can  be  readily  di- 
gested and  appropriated. 

86.  Eating  too  much. — But,  on  the  other  hand, 
we  must  not  teike  too  mucli  food.  There  seems  to  be 
some  subtile  relation  between  the  amount  of  food 
required  by  the  system  and  the  amount  of  gastric 
juice  furnished  by  the  stomach.  What  is  likely  to 
be  the  result,  then,  if  more  food  is  taken  into  the 
stomach  than  can  be  acted  on  by  the  gastric  juice? 
Let  us  consider.  The  temperature  of  the  interior 
of  the  stomach  is  about  ioo°  Fahr.  This  is  just 
about  the  temperature  at  which  fermentation  and 
putrefaction  (which  is  a  sort  of  fermentation)  are 
most  active.     Heat  and  moisture  favor  these  pro- 


7o 


ORGANS  OF  REPAIR. 


cesses.  Both  of  these  conditions  exist  in  the  stom- 
ach, but,  under  ordinary  circumstances,  the  gastric 
juice  prevents  any  other  changes  than  those  due 
to  its  own  action.  But,  if  more  food  is  introduced 
than  the  gastric  juice  can  dissolve,  fermentation 
occurs,  and  offensive  gases  and  irritating  acids  are 
produced.  Then  the  symptoms  of  indigestion  come 
on,  there  is  constant  belching  of  wind  from  the 
mouth,  an  uneasy  sensation  in  the  stomach,  and,  as 
soon  as  the  undigested  and  fermenting  mass  passes 
out  into  the  intestine,  rumblings  and  colic  set  in, 
followed  probably  by  a  diarrhoea,  which  continues 
until  the  offending  matters  have  been  ejected  from 
the  body. 

87.  Eating  between  Meals. — Similar  symptoms 
may  be  produced  by  eating  between  meals.  When  a 
sufficient  meal  has  already  been  eaten,  we  should 
wait  until  it  has  been  digested  and  the  stomach  has 
had  a  short  period  of  rest  before  we  give  it  any 
more  work  to  do.  This  organ  can  not  work  inces- 
santly any  more  than  other  parts  of  the  body,  and 
when  it  is  ready  for  more  food  the  sensation  of 
hunger  apprises  us  of  the  fact.  If  we  load  it  with 
fresh  food  before  the  previous  supply  has  been  dis- 
posed of,  there  may  not  be  enough  gastric  juice 
secreted  to  digest  it.  Then  it  ferments,  or  putre- 
fies, and  causes  a  fit  of  indigestion,  as  just  described. 

88.  Hunger. — It  is  sometimes  said  that  a  person 
should  rise  from  the  table,  after  every  meal,  still 
hungry.  This  is  not  correct,  and  the  reason  is 
plain.  Hunger  is  the  natural  indication  that  the 
body  is  beginning  to  be  worn  out,  and  needs  fresh 
material  to  repair  its  losses.  And  although  the 
appropriation  of  the  food  is  finally  made  by  the 


STOMACH-DIGESTION.  yi 

cells  that  compose  the  body,  and  so  must  be  after 
it  has  been  already  digested  and  carried  to  them, 
nevertheless  the  sympathy  of  the  different  parts  of 
the  body  with  each  other  is  such  that  hunger  is 
satisfied  by  the  mere  act  of  supplying  food  to  the 
stomach.  Not  only  that,  but  the  digestibility  of 
the  food  has  a  great  deal  to  do  with  it.  Certain 
kinds  of  food,  which  we  call  rich,  generally  contain- 
ing a  great  deal  of  fat  and  sugar,  satisfy  the  hunger 
and  produce  a  sense  of  satiety,  when  we  have  not 
really  eaten  enough  to  supply  the  bodily  needs. 
This  is  because  such  food  is  digested  very  slowly, 
being  so  permeated  with  fat  that  the  gastric  juice, 
which  does  not  digest  fat,  penetrates  to  the  albumi- 
nous portions  of  the  food  with  great  difficulty.  In 
such  cases  also  fermentation  frequently  occurs,  and 
persons  who  eat  much  so-called  rich  food  may  satis- 
fy their  hunger  with  it  day  after  day,  and  still  suffer 
from  indigestion,  and  not  get  enough  nourishment 
to  repair  the  waste  of  the  body.  For  these  reasons, 
plain  food  is  the  best,  especially  for  the  young. 

89.  How  much  to  eat. — The  true  way,  there- 
fore, is  not  to  rise  hungry  from  the  table,  but  to 
stop  eating  when  the  hunger  has  been  satisfied,  and 
before  any  feeling  of  repletion  comes  on.  It  should 
be  borne  in  mind  that  the  process  of  digestion 
ought  to  go  on  without  our  consciousness.  After 
a  proper  meal,  the  only  sensation  caused  by  the 
food  Ave  have  taken  should  be  that  of  complete 
satisfaction  and  contentment.  If  the  stomach  feels 
stuffed  and  full,  we  have  eaten  too  much.  It  may 
be  properly  disposed  of  if  the  eater  is  in  vigorous 
health,  and  able  to  rest  for  a  time  until  the  uneasy 
feeling  of  repletion  wears  away.     But  the  whole 


72 


ORGANS  OF  REPAIR. 


process  ought  to  go  on  without  causing  us  a  mo- 
ment's thought.  If  we  are  healthy,  and  if  we  treat 
our  digestive  organs  properly,  we  ought  never  to 
feel  that  we  have  a  stomach,  or  liver,  or  bowels. 
They  will  never  trouble  us,  if  we  do  not  trouble 
them. 

Our  meals,  therefore,  should  be  sufficiently  far 
apart  to  allow  an  hour  or  two  at  least  to  intervene 
between  the  digestion  of  one  meal  and  the  begin- 
ning of  another.  As  digestion  in  the  human  being 
ordinarily  occupies  from  three  to  four  hours,  our 
meals  should  be  at  least  five  hours  apart,  and  this 
is  about  the  time  usually  allowed. 

90.  What  to  eat. — The  matter  of  what  to  eat, 
amid  the  great  variety  of  foods,  may  safely  be  left, 
in  a  healthy  person,  to  the  appetite.  It  is  a  familiar 
proverb  that  "  one  man's  meat  is  another  man's 
poison."  Each  individual  must  learn  for  himself 
what  food  is  the  best  for  him.  If  any  article  is 
found  to  disagree,  it  should  thereafter  be  let  alone ; 
no  attempt  should  be  made  to  overcome  a  natural 
repugnance,  and  acquire  an  appetite  for  what  is 
distasteful.  This  is  to  fly  in  the  face  of  Nature ;  it 
is  much  the  same  as  saying  that  one  is  competent 
to  direct  the  secret  processes  of  nutrition  and  to 
regulate  the  functions  of  organs,  about  which  he 
knows  almost  nothing,  and  which  he  can  not  con- 
trol. Such  action  is  intermeddling,  not  judicious 
care. 

91.  Condiments.  —  Something  should  here  be 
said,  however,  about  the  use  of  certain  substances 
which  are  not  foods,  and  yet  are  in  common  use 
throughout  the  world,  to  make  food  more  accepta- 
ble to  the  palate.     Such  substances  are  pepper  and 


S  TO  MA  CH-DIGES  TION.  7  3 

mustard.  These  condiments  have  two  qualities 
that  have  caused  them  to  be  used  in  the  prepara- 
tion of  food,  viz.,  a  peculiar  flavor,  which  makes 
articles  of  food  to  which  they  have  been  added 
more  savory,  and  a  quality  called  pungency — i.  e., 
they  irritate  any  part  of  the  body  with  which  they 
are  brought  in  contact.  When  either  is  placed 
upon  the  tongue,  smarting  is  produced,  sometimes 
to  a  painful  degree,  and  tears  start  in  the  eyes. 
The  effect  can  therefore  be  imagined  when  these 
substances  are  rubbed  over  the  delicate  mucous 
lining  of  the  stomach  during  the  movements  of 
digestion.  They  can  not  but  be  extremely  irritat- 
ing, and  therefore  injurious.  As  a  matter  of  fact, 
the  excessive  use  of  such  things,  whether  alone 
or  in  highly-seasoned  sauces  (Worcestershire,  etc.), 
results  in  extreme  debility  of  the  digestive  appara- 
tus and  confirmed  dyspepsia.  The  golden  rule  in 
the  treatment  of  the  stomach  is,  to  put  nothing  into 
it  that  can  be  felt  after  entrance.  As  before  stated, 
the  operations  of  the  stomach  ought  to  go  on  with- 
out our  consciousness  of  them.  If  enough  spice  is 
taken  to  produce  a  feeling  of  warmth  in  that  organ, 
it  is  too  much,  and  the  mucous  membrane  has  been 
irritated.  We  are  all,  or  nearly  all,  born  into  the 
world  with  sound  digestive  organs,  which  need  no 
spurring  to  make  them  do  their,  duty.  If  the)'  get 
out  of  order,  it  is  our  own  fault,  and  rest  will  do 
more  than  anything  else  to  set  them  right.  If  you 
whip  a  good  horse,  when  he  is  doing  his  best,  you 
will  spoil  him. 

92.  The  Natural  Drink. — The  natural  drink  of 
all  animals  is  water,  for  milk  is  to  be  looked  upon 
as  a  food.     Many  people,  however,  are  not  satisfied 


74 


ORGANS  OF  REPAIR. 


with  water  alone,  but  prefer  it  flavored  with  some- 
thing else,  and  a  great  variety  of  drinks  have  been 
invented,  of  which  we  shall  only  consider  tea,  cof- 
fee, and  those  which  contain  alcohol,  as  malt  and 
spirituous  liquors  and  wines. 

93.  Effects  of  Alcohol ;  Intoxication. — Alcohol 
is  a  poison,  and  the  proof  of  this  assertion  is  clear 
when  the  ordinary  effects  of  liquors  containing  it 
are  considered.  When  a  person  takes  so  much  of 
an  alcoholic  drink  that  he  feels  the  effects  of  it,  he 
is  somewhat  exhilarated,  the  pulse  is  quicker  and 
stronger,  the  face  is  flushed,  his  ideas  seem  to  flow 
more  freely,  he  is  more  cheerful  and  happy,  and  he 
seems  brighter  than  before.  And  yet,  even  in  this 
very  first  stage  of  intoxication,  a  close  observer  can 
see  that  a  poisonous  effect  has  been  produced  upon 
his  nervous  system.  His  judgment  is  weakened, 
his  control  over  his  thoughts  is  slightly  lessened, 
and  things,  which  when  strictly  sober  he  conceals, 
often  come  to  the  light  in  his  conversation.  In 
brief,  he  is  beginning  to  lose  the  mastery  of  him- 
self. If  more  alcohol  is  taken,  the  brain  becomes 
more  and  more  oppressed,  he  loses  control  of  his 
muscular  movements,  he  mumbles  in  his  speech, 
talks  nonsense,  and  finally  becomes  unconscious. 
The  poison,  however,  if  enough  has  not  been  taken 
to  kill,  is  gradually  ejected  from  the  body,  through 
the  lungs,  skin,  and  kidnevs,  and  the  paralyzed 
organs  begin  to  recover.  When  consciousness  re- 
turns, the  person  is  dreadfully  sick  with  a  throbbing 
headache  and  nauseated  stomach,  which  only  recover 
their  normal  condition  after  a  more  or  less  pro- 
longed period  of  rest.  Surely  such  effects  are  not 
those  of  a  food,  but  of  a  rank  poison. 


STOMACH-DIGESTION.  75 

94.  Narcotic  Poisons.  —  But  the  more  remote 
effects  of  alcohol  are  even  more  striking  and  of 
greater  importance.  It  is  not  only  a  poison  but  a 
narcotic  poison.  It  belongs  to  the  same  class  with 
opium,  chloroform,  ether,  hydrate  of  chloral,  etc. ; 
the  great  peculiarity  of  which  is,  that  they  never 
leave  the  body,  through  which  they  have  once 
passed,  in  quite  the  same  condition  in  which  they 
found  it.  The  person  who  has  once  taken  them  is 
apt  to  feel  a  desire  to  take  them  again.  And  this 
desire  is  not  like  the  ordinary  appetite  for  food  :  it 
is  not  that  their  taste  or  smell  is  agreeable,  for  as  a 
rule  the  reverse  is  the  case.  It  is  the  after-effect 
that  is  sought.  The  oftener  this  desire  is  gratified, 
the  stronger  it  becomes,  until  finally  the  man  is  no 
longer  master  of  himself,  neglects  his  daily  affairs, 
and  takes  no  interest  in  anybody  or  anything  but 
plans  for  obtaining  a  fresh  supply  of  the  poison. 

95.  First  Symptoms  of  Narcotism. — This  evil 
effect  of  the  narcotic  poisons  does  not  follow  unless 
enough  has  been  taken  to  produce  the  first  symp- 
toms of  narcotism,  which  is  really  the  only  agree- 
able stage,  and  is  characterized  by  a  curious  sort  of 
tingling  all  over  the  body,  somewhat  as  if  the  run- 
ning of  the  blood  could  be  felt  in  the  blood-vessels. 
Indeed,  it  is  probably  caused  by  the  contact  of  the 
alcohol  with  the  millions  of  cells  that  compose  the 
body,  and  is  the  symptom  of  commencing  paralysis.* 
When  this  sensation  is  felt,  too  much  alcohol  has  al- 
ready been  taken,  and  poisoning  has  begun. 

06.  Effect  of  Alcohol  on  Growing  Persons. — Be- 

*  The  flushing  of  the  face  and  the  more  rapid  action  of  the  heart 
are  due  to  the  paralyzing  effect  of  the  alcohol  on  the  vaso-motor 
nerves,  which  will  be  described  hereafter. 


j6  ORGANS  OF  REPAIR. 

sides  this  danger  connected  with  the  use  of  alco- 
holic drinks,  which  is  common  to  them  with  other 
narcotic  poisons,  alcohol  retards  the  growth  of 
young"  cells  and  prevents  their  proper  development. 
Now,  the  bodies  of  all  animals  are  made  up  largely 
of  cells,  as  heretofore  shown,  and,  {he  cells  being  the 
living  part  of  the  animal,  it  is  especially  important 
that  they  should  not  be  injured  or  badly  nourished 
while  they  are  growing.  So  that  alcohol,  in  all 
forms,  is  particularly  injurious  to  young  persons,  as 
it  retards  their  growth,  and  stunts  both  body  and 
mind. 

97.  Effect  of  Habitual  Excess  in  the  Use  of  Al- 
cohol.— When  alcohol  is  used  habitually  in  quanti- 
ties sufficient  to  produce  symptoms  of  poisoning,  it 
causes  serious  changes  in  many  parts  of  the  body, 
especially  in  the  stomach,  liver,  kidneys,  and  blood- 
vessels. The  habitual  drinker  is  therefore  never  in 
good  health,  and  never  lives  to  be  old.* 

98.  Alcohol  diminishes  the  Power  of  Endurance. 
— It  has  been  amply  shown  by  Arctic  explorations 
and  by  military  campaigns  in  India  and  Africa, 
that  those  who  use  no  alcohol  endure  privation, 
fatiguing  labor,  and  extremes  of  temperature  much 
better  than  those  who  take  daily  rations  of  grog. 
The  common  opinion  that  alcoholic  liquors  ward  off 
the  cold  and  temper  the  heat  arises  from  the  fact 
that  the  bodily  sensations  are  dulled  by  the  narcotic ; 

*  It  is  not  to  be  inferred,  from  what  has  been  said,  that  every  person 
who  uses  alcoholic  stimulants  will  become  a  drunkard,  but  it  can  not  be 
denied  that  every  such  person  runs  a  risk  of  becoming  one.  Not  every 
one  who  goes  into  battle  is  killed  or  even  wounded,  but  every  one  in- 
curs danger.  Alcoholic  drinks  are  not  necessary  to  healthy  persons, 
and  the  habitual  use  of  them  is  like  playing  with  fire  near  a  keg  of 
gunpowder.     No  harm  may  result,  but  it  is  a  foolish  thing  to  do. 


STOMACH-DIGESTION.  yy 

the  drinker,  in  other  words,  is  partially  anaesthe- 
tized, so  that,  although  he  feels  cold  and  heat  in  a 
less  degree,  he  is  really  less  able  to  resist  them. 

It  is  found,  also,  that  even  moderate  drinkers 
are  more  likely  to  be  attacked  by  epidemic  dis- 
eases, that  they  do  not  bear  surgical  operations  so 
well,  that  they  suffer  more  from  exposure  of  any 
kind,  and  that  they  are  apt  to  succumb  to  diseases 
from  which  the  abstinent  generally  recover. 

99.  Tea  and  Coffee. — Tea  and  coffee  are  found 
to  stimulate  the  nervous  system,  producing  slight 
exhilaration  and  relieving  exhaustion  without  the 
subsequent  depression  that  follows  the  use  of  alco- 
hol. In  excess,  however,  they  produce  nervous 
disorders,  and,  although  the  moderate  use  of  them 
is  not  harmful  to  adults,  their  influence  upon  the 
nerves,  the  most  impressionable  part  of  a  growing 
person,  renders  them  unsuitable  articles  of  diet  for 
the  young.* 

100.  Confectionery. — Confectionery  is  not  injuri- 
ous, when  pure,  unless  taken  in  excess.  Unfortu- 
nately, it  is  frequently  adulterated,  and,  instead  of 
containing  simply  sugar,  flour,  gum-arabic,  and 
such  harmless  substances,  is  mixed  with  terra  alba 
(gypsum),  because  it  is  heavy  and  cheap.     Poison- 

*  Of  tobacco,  it  may  be  said  that,  although  it  is  a  poisonous  weed, 
and,  when  first  used,  produces  alarming  symptoms  of  nervous  prostra- 
tion, it  is  soon  tolerated  by  the  system,  and  becomes  a  source  of  great 
comfort  and  satisfaction  to  those  who  use  it  habitually.  The  excessive 
secretion  of  saliva,  however,  in  those  who  chew  it,  produces  extreme 
thirst,  and  may  thus  lead  to  the  habitual  use  of  alcoholic  stimulants  ; 
while  tobacco-smoke,  constantly  irritating  the  mucous  membrane  of  the 
throat  and  nose,  produces  chronic  catarrh  of  those  parts.  It  is  said 
that  no  habitual  smoker  has  a  healthy  throat.  It  has  been  abundantly 
shown  that  the  habitual  use  of  tobacco  stunts  the  growth,  and  it  should 
therefore  be  shunned  by  the  young. 


78  ORGANS  OF  REPAIR. 

ous  coloring-matters  are  also  used.  All  candy  that 
has  a  gritty  feeling  in  the  mouth  should  be  rejected, 
and  bright-yellow,  orange,  and  green  candies  are 
to  be  looked  on  with  suspicion,  for  they  are  almost 
always  colored  with  chromate  of  lead. 

101.  Danger  of  Parasites  in  Food. — A  word  of 
caution  is  necessary  about  the  eating  of  pork.  This 
meat  occasionally  contains  millions  of  minute  para- 
sitic worms,  called  the  trichi'na  spira'lis,  and,  if  such 
meat  is  eaten  without  killing  these  worms,  they  are 
set  free  in  the  alimentary  canal,  bore  their  way  into 
the  blood-vessels,  and  are  carried  by  the  current  of 
blood  all  over  the  body.  When  they  come  to  ves- 
sels so  small  that  they  can  not  pass,  they  are  stuck, 
dam  up  the  blood-current,  interfere  with  the  circu- 
lation, and  produce  serious  and  often  fatal  disease. 
These  parasites  are  killed  by  a  temperature  of  1600 
Fahr.,  and  pork,  therefore  (including  ham,  of  course), 
should  never  be  eaten  unless  it  is  thoroughly 
cooked.* 

Briefly,  then,  to  keep  the  stomach  healthy,  masti- 
cate the  food  thoroughly,  eat  when  you  are  hungry, 
avoid  overeating  and  eating  between  meals,  eat  plain 
food,  do  not  spur  the  stomach  with  condiments  or  appe- 
tizers, and  use  alcoliolic  drinks  and  tea  and  coffee,  if  at 
all,  with  the  greatest  moderation  and  caution. 

*  The  flesh  of  the  pig  occasionally  contains  another  parasite,  called 
the  cysticer'cus  celluld see,  which,  if  taken  alive  into  the  stomach,  devel- 
ops into  the  tape-worm.  This  parasite,  like  the  trichina,  is  killed  by 
thorough  cooking. 


CHAPTER   IV. 

INTESTINAL  DIGESTION. 

102.  The  Chyme. — After  the  partially  digested 
food  has  passed  out  of  the  stomach  into  the  intes- 
tine, it  undergoes  still  further  changes,  and  the 
difficulties  of  investigation  in  this  part  of  the  body 
are  so  enormous  that  very  little  progress  has  been 
made  toward  a  clear  explanation  of  what  takes 
place  there.  Enough  has  been  learned,  however, 
to  give  us  a  general  idea  of  how  the  process  of  di- 
gestion is  completed. 

We  have  seen  that  the  fats  and  the  starches 
are  not  digested  in  the  stomach.  The  gastric  juice 
does  not  act  upon  them  at  all,  and  they  pass  into 
the  intestine  in  very  much  the  same  condition  in 
which  they  enter  the  stomach.  The  fibers  and  tis- 
sues which  hold  the  fats  and  starches  together, 
being  nitrogenous  in  their  nature,  are  acted  upon 
in  the  stomach  and  dissolved,  so  that  the  fat  is  set 
free  and  floats  in  globules  like  those  upon  the  sur- 
face of  a  kettle  of  soup.  The  food  thus  prepared 
to  pass  into  the  intestine  forms  a  thick,  turbid,  gray- 
ish fluid,  called  the  chyme. 

103.  The  Intestines. — The  small  intestine,  into 
which  the  food  passes  from  the  stomach,  is  a  tube 
about  twenty  feet  in  length,  and  an  inch  in  diame- 


8o 


ORGANS  OF  REPAIR. 


ter.  It  is  composed,  like  the  stomach,  of  three 
layers,  the  innermost  one  being  mucous  membrane, 
the  middle  one  muscular  fibers,  some  of  Avhich  are 
circular  and  some  longitudinal,  and  the  outer  layer 
serous  membrane.* 

The  small  intestine  is  connected  with  the  large 
one  by  a  valve-like  opening  situated  in  the  vicinity 
of  the  right  groin.  The  large  intestine  passes  from 
this  point  upward  to  the  liver,  thence  across  to  the 
left  side,  and  then  downward,  constituting  the  last 
five  feet  of  the  alimentary  canal. f 

104.  Muscular  Fibers  of  Intestine. — The  muscular 
fibers  of  the  intestine  contract  with  a  worm-like 
motion,  which  always  begins  near  the  stomach,  and 
extends  slowly  along  the  whole  length  of  the  intes- 
tine, gradually  emptying  it  of  its  contents.     In  this 

*  The  outer  membrane  of  the  in- 
testine of  animals,  when  separated  from 
the  rest,  is  used  for  sausage-casings, 
and,  when  properly  prepared,  also 
makes  what  is  called  gold-beater's  skin. 
\  The  beginning  of  the  large  intes- 
tine is  situated  in  the  right  groin,  and 
forms  a  sort  of  bag  or  pouch,  called 
the  ccBcum.  From  one  side  of  this 
pouch  there  projects  a  slender  tube  re- 
sembling the  intestine  in  structure,  and 
about  six  inches  long.  This  is  called 
the  appendix  vermiformis,  i.  e.,  the 
worm-like  appendage  (Fig.  27).  In 
man  it  seems  to  be  entirely  useless,  and 
is  in  fact  a  constant  source  of  danger  ; 
for  occasionally  small  objects,  like 
cherry-pits  and  grape-seeds,  which  are 
swallowed  with  the  food  and  not  di- 
gested, become  lodged  in  it,  and  grad- 
ually produce  an  irritation  which  results  in  an  abscess,  and  destroys 
life.     Such  cases  are  not  uncommon  in  medical  practice. 


Fig.  27. — Junction  of  the  small 
and  large  intestines,  and  the 
appendix  vermiformis.  The 
large  intestine  (here  called  the 
ctzcum)  is  cut  away  so  as  to 
show  the  internal  openings. 


INTESTINAL  DIGESTION. 


8l 


slow  passage  of  the  food  from  the  stomach  through 
the  small  intestine  to  the  large  one,  it  is  mingled 
with  various  fluids  which  complete  the  process  of 
digestion,  and  the  nutritious  portions  of  the  mass 
are  absorbed  and  carried  away  by  the  blood  and 
other  vessels. 

105.  The  Duodenum.  —  The  first  eight  or  ten 
inches  of  the  small  intestine  are  somewhat  larger 
than  the  remainder,  and  are  called  the  duode' uum, 
because  its  length  is  about  twelve  fingers'  breadth. 
Into  this  duodenum  empty  small  canals  from  two 
very  important  organs,  viz.,  the  pan'crcas  and  the 
liver. 

106.  The   Pancreas.  —  The   pancreas  (Fig.  28), 


Fig.  28. — The  pancreas,  partly  cut  away,  so  as  to  show  the  duct,  which 
collects  the  pancreatic  juice,  and  empties  it  into  the  duodenum. 

which  we  call  the  sweet-bread  when  we  cook  it  for 
food,*  is  about  six  inches  long,  is  shaped  somewhat 

*  There  are  three  kinds  of  sweat-breads,  viz.  :  the  thyroid-gland, 
or  throat  sweet-bread,  which  is  tough,  almost  like  India-rubber  ;  the 
pancreas,  or  belly  sweet-bread,  which  is  more  tender,  and  is  quite  com- 
monly used  ;  and  the  thymus-gland,  or  breast  sweet-bread,  which 
exists  only  in  young  animals,  wasting  away  as  they  grow  up.  This 
gland  is  situated  just  behind  the  upper  portion  of  the  breastbone,  at- 
tains its  greatest  size  in  human  beings  at  the  age  of  two  years,  and 
disappears  before  the  sixteenth  year.      Its  use  is  not  known.     This 


82  ORGANS  OF  REPAIR. 

like  a  pistol,  and  is  situated  behind  the  stomach, 
with  the  large  end,  or  the  breech  of  the  pistol, 
toward  the  right.  It  secretes  a  fluid,  called  the 
pancrcat'ic  juice,  which  has  been  shown  to  be  the 
chief  agent  in  the  digestion  of  the  fatty  portions  of 
the  food.  If  a  quantity  of  oil  be  shaken  up  with  pan- 
creatic juice,  a  white,  opaque,  creamy  fluid  is  formed, 
in  which  the  drops  of  oil  or  fat  are  not  visible  any 
more  than  they  are  in  ordinary  milk  or  cream.  Mi- 
croscopic examination,  however,  shows  that  the  oil 
is  not  in  any  way  decomposed,  but  is  divided  into 
very  minute  particles,  in  which  condition  it  can 
be  absorbed  by  the  proper  channels.  In  this  way 
fat  is  taken  up  into  the  circulating  fluids  in  its  own 
proper  form,  and  does  not  undergo  decomposition 
until  it  reaches  other  parts  of  the  body,  if  at  all. 
The  pancreatic  juice  also  liquefies  the  nitrogenous 
matters  which  may  have  passed  the  pylorus  undi- 
gested, as  well  as  the  starches.  In  fact,  it  seems  to 
be  the  chief  agent  in  completing  the  act  of  diges- 
tion, which  has  begun  in  the  stomach. 

107.  The  Liver.  —  The  liver  (Fig.  29)  is  a  very 
large  organ,  the  largest  and  heaviest  in  the  body, 
weighing  in  a  healthy  adult  from  three  to  four 
pounds,  and  situated  on  the  right  side,  protected  by 
the  lower  four  or  five  ribs.  It  secretes  the  bile,  and 
from  its  size,  and  the  amount  of  its  secretion,  is 
evidently  one  of  the  most  important  organs  in  the 
body,  and  yet  its  precise  use  is  still  a  matter  of  dis- 
pute and  doubt. 

108.  Liver-Sugar. — It  was  long  supposed  that  the 
only  function  of  the  liver  was  to  secrete  the  bile ;  but 

gland,  taken  from  calves  and  lambs,  is  the  most  tender  and  palatable 
sweet-bread  of  all. 


INTESTINAL  DIGESTION. 


83 


it  has  been  found,  in  recent  years,  that  it  also  forms 
a  kind  of  sugar  in  large  amount.  The  blood  which 
enters  the  liver  is  found  to  contain  a  small  amount 


Fig.  29. — Under  surface  of-  the  liver. 


of  sugar,  while  that  which  flows  away  from  it,  after 
having  circulated  through  it,  always  contains  sugar 
in  considerable  quantity.  Even  this  fact,  well  estab- 
lished as  it  seems  to  be,  is  still  a  subject  of  dispute 
among  experimental  physiologists. 

109.  The  Bile. — The  bile  is  a  somewhat  glutinous 
fluid,  of  a  rich,  golden-red  color,"  which  is  dis- 
charged into  the  duodenum  through  the  same  open- 

*  When  vomiting  takes  place  and  lasts  for  a  time,  the  intestines 
reverse  their  action,  and  bile  is  carried  backward  through  the  pylorus 
into  the  stomach.  It  is  here  out  of  place,  and  produces  extreme  nausea. 
Its  color  is  changed  by  the  gastric  juice  to  a  greenish  yellow. 


84  ORGANS  OF  REPAIR. 

ing  with  the  pancreatic  juice.*  It  must,  therefore, 
become  mingled  with  the  food  long  before  digestion 
is  completed.  The  natural  inference  from  this  is 
that  it  has  something  to  do  with  the  process ;  but 
the  digestion  of  every  portion  of  the  food  can  be 
accounted  for  in  other  ways.  Nitrogenous  matters 
are  digested  in  the  stomach,  while  the  fatty  mat- 
ters and  the  starches  are  digested  by  the  pancre- 
atic juice,  assisted,  perhaps,  by  the  intestinal  juices, 
to  be  hereafter  spoken  of.  It  would  appear,  then, 
that  there  is  nothing  left  for  the  bile  to  do,  and 
that  it  must  be  an  excrementitious  fluid —  i.  e.,  that 
it  consists  of  matters  which  have  been  separated 
from  the  blood  by  the  liver  because  they  are  hurt- 
ful to  the  organism,  and  must,  therefore,  be  ex- 
pelled from  the  body.  This  was  the  ancient  view, 
and  it  seemed  to  be  supported  by  the  fact  that,  if 
the  liver  be  diseased  so  that  this  separation  can 
not  take  place,  and  the  constituents  of  the  bile  re- 
main in  the  blood,  jaundice  occurs,  and,  if  there  is 
no  relief,  the  person  dies  with  all  the  symptoms 
of  poisoning.  So  far,  it  seems  plain  enough  that 
the  bile  has  no  office  to  perform  in  the  body,  but 
is  only  secreted  to  be  expelled.  But  operations 
have  been  performed  on  animals  in  such  a  way  that 
the  action  of  the  liver  should  not  be  interfered  with, 
and  yet  the  bile  should  not  enter  the  intestine,  but 
should  be  discharged  outside  the  body  through  an 
artificial   opening.      Under  such   circumstances,  if 

*  As  soon  as  the  partially  digested  food,  containing  a  certain  amount 
of  gastric  juice,  passes  the  opening  of  the  bile-duct,  there  is  a  great 
gush  of  bile  into  the  intestine.  It  is  found  that  any  acid,  applied  to  this 
opening,  will  produce  the  same  effect.  The  bile,  being  alkaline,  neu- 
tralizes the  gastric  juice,  which  is  therefore  of  no  further  use,  and  so 
the  digestive  process  has  to  be  completed  by  other  means. 


INTESTINAL  DIGESTION.  85 

the  bile  be  simply  an  excrementitious  fluid,  its  dis- 
charge from  the  body  by  one  channel  rather  than 
by  another  ought  not  to  make  any  difference  in  the 
health  of  the  animal.  But  it  is  found,  on  the  con- 
trary, that  animals  treated  in  this  way  die  with 
every  appearance  of  starvation.  Their  appetite  re- 
mains good,  their  digestion  is  not  interfered  with ; 
but,  nevertheless,  although  they  eat  ravenously,  and 
are  plentifully  supplied  with  food,  they  become 
rapidly  emaciated  and  die  in  about  a  month. 
These  facts  show  conclusively  that  the  bile  has 
some  important  part  to  play  in  the  nutrition  of  the 
body. 

It  is  found,  moreover,  by  actual  chemical  exami- 
nation of  the  excretions,  that  the  bile,  although  it 
is  discharged  into  the  intestine,  does  not  all  leave 
the  body.  It  must,  then,  be  reabsorbed  into  the 
circulation.  But,  if  this  be  so,  why  does  it  not  give 
rise  to  symptoms  of  poisoning,  just  as  if  it  were 
prevented  from  leaving  the  blood  in  the  first  place  ? 
The  only  possible  answer  to  this  is,  that  it  is  some- 
how changed  in  the  intestine,  so  that  when  it  is 
reabsorbed  it  is  harmless. 

no.  The  Intestinal  Juices. — Besides  the  bile 
and  pancreatic  juice,  the  food  meets  in  the  small 
intestine  with  the  intestinal  juices  proper.  Of  these 
very  little  is  known  with  certainty,  owing  to  the 
great  difficulty  of  obtaining  them  from  the  living 
animal  unmixed  with  other  fluids.  The  small  in- 
testine is  lined,  however,  with  a  mucous  membrane 
containing  millions  of  small  tubules  and  glands, 
which  secrete  certain  colorless  alkaline  fluids.  Of 
these  fluids  it  is  both  affirmed  and  denied  that  they 
possess  the  property  of  turning  starch  into  sugar 
5 


86  ORGANS  OF  REPAIR. 

with  great  rapidity ;  but,  so  far  as  is  known,  their 
part  in  the  process  of  digestion  is  not  important. 

in.  Absorption  of  Food. — If  animals  are  killed 
at  different  times  after  the  eating  of  food,  and  dif- 
ferent portions  of  the  intestine  are  examined,  it  is 
found  that,  while  the  upper  portion  of  the  small 
intestine  contains  a  large  amount  of  partially-di- 
gested  food,  the  lower  portion  contains  the  shriv- 
eled remnants  of  muscular  tissue,  the  husks  of 
grains,  the  woody,  indigestible  fibers  of  vegetables, 
etc. ;  in  short,  the  unappropriated  residue  of  the 
food  which  has  been  taken.  The  great  mass  of 
what  has  been  eaten  has  disappeared,  and  after  a 
certain  time  the  whole  intestine  will  be  found 
empty.  There  are  two  systems  of  vessels  by  which 
this  absorption  of  food  is  accomplished — they  are 
the  blood-vessels  and  the  lacteals* 

112.  The  Peritonaeum. — To  understand  the  ar- 
rangement of  these  vessels,  it  is  necessary  to  know 
something  of  the  peritonce'iim.  The  serous  mem- 
brane, which  has  been  spoken  of  as  covering  the 
outside  of  the  stomach  and  intestines,  covers  to  a 
greater  or  less  extent  all  of  the  organs  contained 
in  the  abdomen,  and  also  lines  the  abdominal  walls. 
This  smooth,  satiny  membrane  is  called  the  peri- 
tonaeum, and  it  renders  the  movements  of  the  ab- 
dominal organs  possible  without  discomfort  to  the 
rest  of  the  organism.  Now,  the  intestine  being,  as 
has  been  shown,  a  long,  narrow  circular  tube,  or 
canal,  and  the  peritonaeum  passing  entirely  around 
it,  there  is  a  line  running  the  whole  length  of  the 

*  Lacteals,  from  a  Latin  word  meaning  milk,  because  when  they 
are  filled  with  the  products  of  digestion  they  look  as  if  they  were  filled 
with  milk. 


INTESTINAL  DIGESTION. 


87 


intestine,  where  the  membrane  becomes  double, 
and  this  double  fold  is  brought  together  like  the 
gathers  of  a  dress,  and  attached  to  the  spinal  col- 
umn. So  the  intestine  is  loose  in  the  abdomen,  and 
still  has  an  attachment  to  the  spinal  column.  Be- 
tween these  two  folds,  or,  in  other  words,  within 
the  double  fold,  between  the  two  layers  of  mem- 
brane, the  blood-vessels  and  lacteal  vessels  pass  to 
the  intestine  (Fig.  30). 


Fig.  30. — Diagram  representing  across  section  of  the  small  intestine,  show- 
ing the  three  layers,  and  the  way  in  which  the  blood-vessels  pass  be- 
tween the  two  folds  of  serous  membrane  (the  peritonaeum). 

These  vessels  grow  smaller  and  smaller  and 
more  and  more  numerous  as  they  approach  the 
intestine,  and,  when  they  at  length  enter  its  walls 
and  penetrate  to  the  mucous  membrane,  they  di- 
vide into  vessels  so  exceedingly  minute  as  to  be 
invisible  to  the  naked  eye,  and  fill  the  interior  of 
the  little  projections  of  the  mucous  membrane, 
which  are  called  villi. 

113.  The  Intestinal  Villi. — The  villi  are  small 
projections  on  the  surface  of  the  mucous  mem- 
brane, about  a  thirtieth  of  an  inch  long,  and  thickly 


88 


ORGANS  OF  REPAIR. 


covering  the  whole  interior  of  the  intestine,  there 
being  about  ten  thousand  of  them  to  the  square 
inch,  and  about  four  million  altogether  (Fig.  31). 

Each  villus  is  covered 
with  epithelium,  and  in 
its  interior  is  a  compli- 
cated mass  of  blood-ves- 
sels, twisted  and  knotted 
like  a  bunch  of  earth- 
worms (Fig.  32).  In  the 
very  center  of  the  whole 
is  an  open  space,  which 
is  the  commencement  of 
a  lacteal. 

114.  The  Lacteal 
Vessels.  —  The  lacteals 
are  only  a  part  of  a  sys- 

FIG  31-Section  of  the  mucous  mem-     tem  Qf  vessel      caU    d  th 
brane  of  the  small  intestine,  show-  §  '  # 

ing  two  villi,  and  several  secreting     fymphat' US, which extend 

tubes  or  follicles;  also  lacteals,    every  where  throughout 

the  body.  The  lym- 
phatics all  begin  in  a 
way  that  is  not  clearly  understood,  and  gradually 
unite  to  form  larger  and  larger  vessels,  until  their 
contents  are  finally  discharged  into  the  veins  and 
mingled  with  the  blood.  The  fluid  found  in  the 
lymphatics,  called  lymph,  is  yellowish,  transparent, 
and  saltish,  and  is  presumed  to  be  derived  in  some 
way  from  the  change  constantly  taking  place  in  the 
tissues.  At  certain  intervals  in  their  course,  the 
lymphatic  vessels  are  interrupted  by  small  bodies 
called  glands*  varying  in  size  from  a  hemp-seed  to 


blood-vessels,  and,  at  the  bottom, 
the  muscular  layer. 


*  The   lymphatic   glands  are  the  bodies  that  sometimes  undergo 


INTESTINAL   DIGESTION. 


89 


an  almond,  into  which  the  vessels  enter,  and  from 
which  they  emerge.  Whether  they  actually  pass 
through  the  gland,  or  whether 
one  vessel  ends  in  it  and  another 
begins,  is  still  a  subject  of  dis- 
cussion. But  the  lymphatic  ves- 
sels all  over  the  body  have  great 
absorbing  power,  taking  up  in- 
discriminately foods,  poisons,  or 
the  waste  of  used-up  tissues. 

The  lactcals,  then,  are  that 
portion  of  the  lymphatic  system 
which  is  connected  with  the 
small  intestine,  and  all  the  lac- 
teals  from  the  villi  gradually 
unite  to  form  a  vessel  called  the 
tJwi-ac'ic  duct,  about  as  large  as  a 
goose-quill,  which  passes  up 
close  to  the  spine,  and  empties 
into  a  large  vein  very  near  the 
heart.* 

115.  The  Portal  Vein. — The 
blood-vessels  which  absorb  the  food  from  the  intes- 
tines are  veins,  and  they  unite  with  the  veins  from 
the  stomach,  pancreas,  and  spleen,  to  form  one  large 
vein,  called  the  portal  vein,  which  enters  the  liver, 
so  that  all  the  blood  from  the  digestive  apparatus 

slow  inflammation  in  persons  of  a  scrofulous  tendency,  forming  hard 
lumps  or  abscesses  in  the  neck. 

*  Many  years  ago,  a  man  named  Calvin  Edson  became  extremely 
emaciated  without  any  known  cause.  He  was  exhibited  for  a  long 
time  as  "  the  living  skeleton."  After  his  death  it  was  found  that  his 
thoracic  duct  was  completely  obstructed,  so  that  none  of  the  contents 
of  the  lacteals  could  pass  into  the  blood.  He  died,  therefore,  of  fat- 
starvation — i.  e.,  a  complete  or  almost  complete  deprivation  of  fat. 


Fig.  32. — Intestinal  villus, 
showing  the  epithelial 
cells  outside,  the  blood- 
vessels, and  the  begin- 
ning of  a  lacteal  vessel. 


9o 


ORGANS  OF  REPAIR. 


passes  through  the  liver  before  it  enters  the  general 
circulation. 

116.  The  Chyle. — The  villi,  then,  projecting  as 
they  do  into  the  interior  of  the  small  intestine 
through  its  entire  length,  are  continually  bathed, 
during  digestion,  in  the  nutritious  fluid  which  other 
organs  have  prepared  for  absorption.  They  float 
and  sway  about  in  this  fluid,  and  suck  it  up  as  the 
roots  of  a  tree  get  their  sustenance  from  the  soil,* 
and  the  blood-vessels  probably  have  quite  as  much 
to  do  in  the  process  as  the  lacteals.  The  latter  ab- 
sorb mostly  the  fatty  matters  in  the  cream-like  form 
to  which  they  have  been  reduced  by  the  pancreatic 
juice.  As  the  walls  of  the  vessels  are  thin  and 
transparent,  the  creamy  contents,  called  the  ckyle, 
show  through,  and  hence  arises  the  white  appear- 
ance during  digestion  which  has  given  them  the 
name  of  lacteals. 

117.  Changes  in  the  Blood  during  Digestion. — 

*  The  latest  researches  seem  to  show  that  the  lacteal  begins  in  the 
interior  of  the  villus  as  a  sort  of  hollow  space,  without  any  special 
wall  of  its  own,  and  that  around  this  space  there  are  small  fibers  of  in- 
voluntary muscular  tissue.  It  is  believed  that,  during  the  process  of  ab- 
sorption, these  muscular  fibers  contract  at  regular  intervals.  The  effect 
of  the  contraction  would  be  to  pull  down  the  top  of  the  villus  toward  the 
base,  and  thus  diminish  the  size  of  the  hollow  space  above  referred  to, 
and  empty  its  contents  into  the  lacteal  vessel.  When  the  fibers  relax, 
and  the  hollow  space  expands  to  its  original  dimensions,  the  fluid 
which  has  been  forced  into  the  lacteal  is  prevented  from  being  sucked 
back  again  by  the  valves,  with  which  all  lacteal  vessels  are  provided. 
The  space  is  therefore  filled  again  by  the  fluids  which  surround  the 
end  of  the  villus  in  the  intestinal  canal.  In  this  way,  by  the  alternate 
and  regular  contraction  and  relaxation  of  these  minute  muscular  fibers, 
the  villus  acts  like  a  suction-pump,  and  the  intestine  may  be  looked 
upon  as  lined  with  millions  of  microscopic  suction-pumps,  which  work 
away  during  digestion,  pumping  the  contents  of  the  intestine  into  the 
lacteals,  by  which  they  are  discharged  into  the  blood. 


INTESTINAL  DIGESTION 


91 


As  absorption  goes  on,  the  blood  becomes  more 
and  more  loaded  with  fatty  matters,  which  can 
easily  be  recognized  in  it  in  the  form  of  minute  oily 
drops,  but  all  of  this  blood  passes  through  the  lungs 
before  it  goes  to  the  rest  of  the  body.  In  its  pas- 
sage through  the  lungs,  the  fatty  matters  disappear 
in  some  way,  not  exactly  understood,  and  the  blood 
which  comes  away  from  the  lungs  contains  none. 
After  a  time,  however,  as  digestion  progresses,  the 
blood  is  so  heavily  charged  with  these  oily  matters 
that  they  can  not  all  be  decomposed,  and  a  portion 
remains  and  is  sent  in  the  general  circulation  all 
over  the  body.  If  blood  be  drawn  from  a  man  or 
other  animal  at  this  time  and  allowed  to  stand, 
there  will  be  a  yellowish,  creamy  layer  on  its  top. 

Presently,  however,  the  fat  begins  to  disappear, 
as  digestion  approaches  its  close ;  the  amount  in 
the  blood  gradually  diminishes,  until  it  is  entirely 
gone,  the  lymph  in  the  lacteals  becomes  once  more 
a  transparent  fluid,  and  digestion  is  complete. 

118.  The  Spleen. — At  the  left  extremity  of  the 
stomach,  just  under  the  ninth,  tenth,  and  eleventh 
ribs,  is  an  organ  which  is  to  this  day  a  great  puzzle 
to  physiologists.  It  is  called  the  spleen,  and  is  about 
five  inches  long,  four  wide,  and  an  inch  thick.  It 
is  reddish  in  color,  soft  and  pulpy  in  texture,  with 
a  very  tough  and  strong  fibrous  covering.  It  re- 
ceives its  blood  from  a  very  large  artery,  and  its 
vein,  which  carries  away  the  blood  from  the  organ, 
joins  the  portal  vein,  so  that  the  blood  from  the 
spleen,  like  that  from  the  other  organs  of  digestion, 
passes  through  the  liver,  before  it  reaches  the  heart. 
The  spleen  is  large  in  well-fed  animals,  and  very 
small  and  shrunken  in  starved  ones,  while  in  some 


Q2  ORGANS  OF  REPAIR. 

cases  of  disease,  such  as  fever  and  ague,  it  reaches 
the  enormous  weight  of  twenty  pounds,  and  forms 
an  immense  hard  tumor  in  the  left  side. 

The  facts  just  stated  would  seem  to  imply  that 
the  spleen  has  some  important  office  to  perform  in 
digestion,  but  what  that  office  is  no  one  has  been 
able  to  discover.*  It  is  a  singular  fact  that  the 
spleen  may  be  entirely  removed  from  animals  with- 
out permanent  injury  to  their  health.  This  opera- 
tion has  often  been  done  to  dogs,  and  the  animal 
recovers  from  the  wound  very  rapidly.  He  shows, 
however,  an  enormous  increase  of  appetite,  usually 
gains  considerable  flesh,  and  acquires  an  unnatural 
ferocity  of  disposition.  These  things,  however,  do 
not  seem  to  indicate  that  any  particular  function 
has  been  lost  to  the  body,  and  the  uses  of  the  spleen 
are  still  a  subject  of  earnest  investigation. 

*  The  most  reasonable  theory  about  the  spleen  at  present  seems  to 
be  that  it  has  something  to  do  with  the  destruction  of  old  and  worn- 
out  blood-corpuscles  and  the  formation  of  new  ones. 


CHAPTER  V. 

THE   BLOOD. 

119.  The  Blood. — After  the  nutritious  portions 
of  the  food  have  been  taken  into  the  blood,  they 
pass  through  the  lungs  before  they  go  into  the 
general  circulation.  Before  we  consider  the  respi- 
ration, however,  it  is  necessary  to  know  something 
of  the  circulating  fluid. 

The  blood  is  a  thick,  opaque  fluid,  varying  in 
color  in  different  parts  of  the  body  from  a  bright 
scarlet  to  a  dark  purple  or  even  almost  black.  It 
has  a  somewhat  viscid  feel,  a  faint  odor  peculiar  to 
itself,  and  a  saltish  taste. 

120.  The  Red  Blood-Corpuscles. — If  a  drop  of 
blood  be  placed  under  the  microscope,*  immense 
numbers  of  small  bodies  will  be  seen,  which  are 
called  the  blood-corpuscles  (Figs.  33  and  34).  They 
are  very  minute,  averaging  only  gg1^  of  an  inch  in 
diameter,  and  are  flattened  in  their  shape.  They 
may  be  described  as  looking  like  a  cylindrical  ring, 
the  center  of  which  has  been  filled  up,  but  not  quite 
to  the  level  of  the  border,  so  that  there  is  a  slight 
depression  on  each  flattened  side.     Taken  singly, 

*  Prick  the  end  of  the  finger  with  a  pin.  The  most  minute  drop 
of  blood  is  sufficient.  Put  it  on  a  glass  slide  under  a  thin  glass  cover, 
and  place  it  under  a  microscope. 


94 


ORGANS  OF  REPAIR. 


these  bodies,  called  the  red  blood-corptiscles,  are  of  a 
light  amber  color,  but  in  a  large  mass  they  give 

the  characteristic  red  col- 
or to  the  blood.  They  vary 
somewhat  in  size  in  differ- 
ent animals,  those  of  the 
monkey  approaching  most 
nearly  to  those  of  the  hu- 
man being.  In  birds,  rep- 
tiles, and  fish,  they  are 
very  much  larger,  and  in- 
stead of  being  circular  are 
oval  (Fig.  35).*  They  also 
have  a  distinct  nucleus. 
It  is  mainly  by  these  microscopical  differences  that 
the  blood  of  different  animals  can  be  distinguished 


Fig.  33. — Human  blood-corpuscles, 
including  two  white  ones. 


Fig.  34. — Human  blood-corpuscles  (highly  magnified).    From  a  photograph. 


*  The  blood-corpuscles  of  the  camel  tribe  are  also  oval,  but  smaller 
than  those  of  birds. 


THE  BLOOD. 


95 


*&■'■>. 


WHITE 


Yig.  35. — Blood-corpuscles  of  the 
frog. 


from    that  of   man,  as   is  sometimes   necessary  in 
trials  for  murder. 

121.  The  White  Blood-Corpuscles. — The  blood 
also  contains  white  corpus- 
cles in  the  proportion  of  one 
white  corpuscle  to  three 
hundred  red  ones.  They 
are  larger  than  the  red,  are 
perfectly  colorless,  and  glo- 
bular in  their  form.  The 
white  corpuscles,  under 
proper  conditions,  are  seen 
to  be  continually  changing 
their  form,  almost  like  liv- 
ing animals.  There  have 
been  many  speculations  as 

to  their  office  in  the  body,  but  nothing  definite  has 
been  ascertained.  In  certain  diseases,  however, 
they  are  found  to  increase  enormously  in  number, 
and  some  of  these  diseases  are  among  the  most 
dangerous  and  difficult  to  treat  of  any  the  physi- 
cian meets  with. 

Although  the  blood-corpuscles  are  so  very  mi- 
nute, they  exist  in  such  enormous  numbers  that 
they  are  estimated  to  compose  half  the  mass  of 
the  blood. 

122.  The  Plasma. —  The  fluid  portion  of  the 
blood,  in  which  these  small  bodies  float,  is  called 
the  plasma.  It  is  almost  colorless,  quite  transpar- 
ent, and  is  nine  tenths  water.  Its  two  most  im- 
portant ingredients  are  albumen  and  fibrin.*     The 

*  It  is  now  believed  that  fibrin  does  not  exist,  as  such,  in  fluid 
blood,  but  that  there  are  certain  substances  (known  as  fibrino-plastin 
or  paraglobtdin,  fibrinogen,  and  fibrin-ferment)  which,  by  their  inter- 


96  ORGANS  OF  REPAIR. 

former  of  these  is  chiefly  concerned  in  nutrition, 
and  the  latter  brings  about  the  remarkable  phe- 
nomenon known  as  coagulation.  The  plasma  also 
contains  various  compounds  of  lime,  soda,  mag- 
nesia, etc.,  which  have  their  own  functions  to  per- 
form in  the  nourishment  of  the  body. 

123.  Coagulation  of  the  Blood.  —  If  blood  be 
drawn  from  the  living  body,  it  very  soon  under- 
goes coagulation.  This  is  due  to  its  fibrin  (or  fibrin- 
factors)  ;  but  the  cause  of  the  change  is  very  im- 
perfectly understood.  After  the  blood  has  stood 
for  a  few  minutes  outside  the  blood-vessels,  it  at 
first  becomes  less  fluid  and  assumes  somewhat  the 
appearance  of  jelly.  Shortly  the  fibrin  begins  to 
contract  and  occupy  a  smaller  space,  gradually 
squeezing  out  the  portion  of  the  blood  which  still 
remains  fluid.  This  mass  which  separates  from  the 
rest  of  the  blood  is  called  the  clot,  and  the  remainder, 
or  still  fluid  portion,  is  called  the  scrum.  The  con- 
traction of  the  clot  continues  for  several  hours, 
until  it  forms  quite  a  firm  mass  of  a  deep-red  color, 
the  remaining  fluid  being  transparent  and  nearly 
colorless. 

The  red  color  of  the  clot  is  due  to  the  fact  that 
the  red  corpuscles  become  entangled  in  the  coagu- 
lated fibrin,  and,  being  semi-solid  in  consistency, 
they  remain  there  and  are  not  pressed  out  with  the 
serum.  It  will  be  noticed  that  the  scrum  is  not  the 
same  as  the  plasma.  The  latter  includes  the  fibrin 
(or  fibrin-factors),  while  the  former  is  without  it. 

124.  Coagulation  under  Varying  Conditions. — It 
is  found  that  the  blood  coagulates  more  rapidly  in 

action,  produce  fibrin,  and  so  cause  coagulation.  The  evidence  for 
this  view  is  of  too  abstruse  a  nature  to  be  given  here. 


THE  BLOOD. 


97 


thin  layers  than  in  a  large  mass ;  in  a  vessel  or  on  a 
surface  which  is  rough  than  in  one  which  is  smooth. 
For  this  reason  the  blood  flows  longer  from  a 
smooth  cut  in  the  body  than  from  a  wound  with 
torn  and  ragged  edges.  In  the  latter  case  the  blood 
coagulates  very  rapidly  and  stops  the  hemorrhage. 

But  the  coagulation  of  the  blood  takes  place  not 
only  outside  the  body,  but,  under  similar  circum- 
stances, inside,  though  not  always  with  equal  ra- 
pidity. If  a  vessel  bursts  inside  the  body,  and 
blood  escapes  into  the  tissues  around  it,  coagula- 
tion takes  place  after  a  short  time ;  and  this  occurs 
even  inside  the  blood-vessels,  if  there  be  any  ob- 
struction to  the  circulation.  If  an  artery  or  vein 
be  compressed  by  a  string  or  wire  or  finger,  the 
blood  will  soon  coagulate  in  the  vicinity  of  the 
pressure.  These  facts  have  suggested  the  means 
used  by  surgeons  to  stop  the  flow  from  a  bleeding 
wound,  and  will  be  referred  to  again. 

125.  Total  Amount  of  Blood. — The  total  amount 
of  blood  in  the  human  body  is  believed  to  be  about 
one  twelfth  of  the  whole  weight  of  the  individual. 
Thus,  in  a  man  who  weighs  one  hundred  and  fifty 
pounds  there  will  be  about  thirteen  pounds  of  blood, 
or  somewhat  more  than  a  gallon  and  a  half. 

126.  Oxygen  in  the  Blood. — This  rich,  nutritious 
fluid  is  forced  to  all  parts  of  the  body  in  a  way  here- 
after to  be  described,  carrying  food  to  exhausted 
tissues  and  removing  the  used-up  matters.  A  large 
part  of  the  material  necessary  for  the  growth  and 
nourishment  of  the  body  is  taken  in  through  the 
digestive,  organs ;  but  there  is  a  gas  absorbed  by 
the  blood,  in  its  passage  through  the  lungs,  which 
is  even  more  necessary  to  life  than  food.     This  gas 


98 


ORGANS  OF  REPAIR. 


is  oxygen,  which  constitutes  about  one  fifth  of  the 
atmosphere,  and  is  essential  to  the  life  of  all  animals, 
probably  without  exception.  We  can  live  for  days 
without  food,  but  we  can  not  live  ten  minutes  with- 
out oxygen.  Even  water-animals  are  not  exempt 
from  this  law;  for  fish  extract  the  air,  which  is  in 
solution  in  the  water,  by  passing  it  through  their 
gills.  If  a  dish  of  water  containing  a  fish  be  placed 
under  the  receiver  of  an  air-pump,  and  the  air  be 
exhausted  from  it,  the  fish  will  be  as  surely  drowned 
as  a  man  would  be  if  held  under  water.  This  is  the 
reason  why  fish  which  are  kept  as  pets  in  aquaria 
need  fresh  water  continually.  If  a  jet  of  water  be 
kept  falling  into  the  vessel  in  which  they  live,  so  as 
to  drag  down  bubbles  of  air,  the  water  need  never 
be  changed,  except  for  cleanliness. 

127.  Varying  Color  of  the  Blood. — The  blood 
which  enters  the  lungs  is  very  dark,  and  sometimes 
almost  black.  When  it  has  passed  through  the 
lungs,  and  flows  away,  it  is  of  a  bright  scarlet.  It 
has  lost  certain  substances  and  gained  others  during 
this  passage,  and  this  beautiful  and  surprising  alter- 
ation is  produced  by  what  is  called  the  process  of 
respiration. 


CHAPTER  VI. 

RESPIRATION. 

128.  Respiration  a  Complicated  Process.  —  At 

first  sight,  the  process  of  respiration  is  a  very  sim- 
ple one,  consisting  merely  in  the  inspiration  and 
expiration  of  air.  In  reality,  however,  it  is  compli- 
cated— certain  very  essential  parts  of  it  going  on 
without  our  consciousness,  like  so  many  of  the  phe- 
nomena of  digestion.  The  organs  mainly  concerned 
in  the  acts  of  respiration  are  the  lungs ;  but  there 
are  certain  additional  organs,  whose  functions,  if  not 
absolutely  necessary,  are  certainly  important. 

129.  The  Nasal  Passages.  —  The  air,  before 
reaching  the  lungs,  goes  through  several  passages, 
lined  throughout  with  mucous  membrane.  The 
human  being  can  breathe  through  either  the  nose 
or  the  mouth  ;  but  in  some  animals  (the  horse,  for 
instance)  respiration  only  takes  place  through  the 
nose,  and,  if  this  be  closed,  suffocation  follows.  The 
external  openings  of  the  nose  are  guarded  by  short, 
stiff  hairs,  which  grow  just  inside  the  nostrils,  and 
which  serve  to  purify  the  air  somewhat,  as  it  passes 
through  them,  by  catching  and  retaining  particles 
of  dust.  The  interior  of  the  nose  is  so  formed  that 
it  is  not  a  large,  open,  free  passage,  but  has  a  num- 
ber of  projecting  bones,  running  lengthwise  along 


100  ORGANS  OF  REPAIR. 

its  walls,  which  are  covered  with  moist  membrane 
and  present  an  extensive  mucous  surface  to  attract 
particles  from  the  air.  If  we  breathe  through  the 
mouth,  on  the  other  hand,  the  air  goes  directly  to 
the  throat,  and  the  cavity  of  the  mouth  is  so  large 
that  the  purifying  effect  of  the  moist  membrane  is 
hardly  perceived.  This  shows  how  much  better  it 
is  to  breathe  always  through  the  nose ;  for  the  air, 
undoubtedly,  in  this  way,  is  rid  of  many  impurities ; 
and  physicians  habitually,  and  almost  unconsciously 
to  themselves,  keep  their  mouths  shut  as  much  as 
possible  when  they  are  exposed  to  a  contagious 
disease. 

From  the  nose  the  air  arrives  at  the  throat,  and 
thence  it  passes  into  the  windpipe,  or  trachea, 
through  a  small  opening  called  the  glottis. 

130.  The  Trachea. — The  tra'chca  (Fig.  36)  is  a 
tube  about  four  and  a  half  inches  long  and  an  inch 
wide,  which  divides  at  its  lower  extremity  into  two 
smaller  tubes  called  bronchi,  one  of  which  goes  to 
each  lung.  It  is  mainly  fibrous  in  its  structure, 
and  it  is  kept  open  to  its  full  extent  by  a  number 
of  rings  of  cartilage,  placed  at  a  short  distance 
apart  through  its  whole  length.  The  trachea  is 
situated  in  the  neck  just  in  front  of  the  oesophagus, 
and  as  these  stiff  rings  might  press  backward  on 
the  oesophagus,  and  thus  interfere  with  the  process 
of  swallowing,  they  do  not  pass  completely  around 
the  trachea,  but  are  lacking  in  the  part  next  the 
oesophagus,  comprising  about  one  third  of  the 
whole  circumference  of  the  tube.  At  the  upper 
extremity  of  the  trachea  is  the  lar'ynx,  or  the  organ 
of  voice,  which  is  essentially  a  triangular-shaped 
box  of  cartilage,  the  lower  end  opening  freely  into 


RESPIRATION. 


101 


the  trachea,  and  the  upper  being  closed  by  muscles 
and  membranous  tissues,  with  the  exception  of  the 
opening  of  the  glottis. 


Fig.  36.— Larynx,  trachea,  and  bronchi,  showing  the  manner  of  division, 
and  the  rings  of  cartilage. 


131.  The  Glottis. — The  glottis  is  a  slit-shaped 
opening,  a  little  less  than  an  inch  long,  extending 
from  before  backward  and  from  above  downward, 


102  ORGANS  OF  REPAIR. 

not  being,  in  other  words,  either  perpendicular  or 
horizontal  in  the  throat,  but  shelving  toward  the 
rear.  The  front  extremity  is  at  the  base  and  back 
of  the  tongue,  and  the  opening  itself  is  bounded  at 
the  sides  by  two  firm,  fibrous,  strong,  pearly-white 
membranes,  called  the  vocal  chords,  by  the  vibration 
of  which  sound  is  produced.  These  vocal  chords 
can  be  separated  to  the  extent  of  half  an  inch,  or 
brought  together  so  as  to  touch,  by  the  muscles 
which  are  attached  to  the  back  part  of  the  larynx. 
The  production  and  modulation  of  the  voice  will 
be  treated  of  hereafter. 

At  the  base  of  the  tongue,  springing  upward 
just  above  the  forward  end  of  the  glottis,  is  a  stiff 
piece  of  cartilage,  shaped  like  a  leaf  with  a  rounded 
end.  This  is  called  the  epiglottis,  and  probably 
performs  two  functions,  viz.,  that  of  protecting  the 
glottis  from  food  or  other  substances  during  the 
act  of  swallowing,  and  that  of  directing  the  column 
of  expired  air  up  toward  the  roof  of  the  mouth 
or  throat,  and  so  aiding  in  the  modulation  of  the 
voice. 

132.  The  Lungs. — The  essential  organs  of  res- 
piration are  the  kings,  which  are  two  in  number  and 
fill  nearly  the  whole  cavity  of  the  chest,  a  portion, 
however,  being  occupied  by  the  heart  and  large 
blood-vessels.  The  lungs  are  very  light  in  propor- 
tion to  their  size,  and  in  animals  they  are  common- 
ly called  "  the  lights."  They  weigh  together  only 
about  two  pounds  and  a  half,  and  easily  float  in 
water.  In  small  children  they  are  of  a  beautiful 
pinkish  color,  but  in  older  persons  they  become 
slate-colored,  and  have  black  spots  scattered  here 
and  there  over  their  surface. 


RESPIRA  TION. 


103 


Fig.  37. — Section  of 
a  pulmonary  lob- 
ule, showing-  its 
division  into  pul- 
monary vesicles. 


133.  Minute  Divisions  of  the  Lungs. — After  the 
trachea  divides  into  two  bronchial  tubes,  one  of 
which  goes  to  each  lung,  these  bron- 
chial tubes  continue  to  subdivide  in- 
to smaller  and  smaller  tubes,  all  the 
branches  diverging  widely  from 
each  other,  until  their  diameter  is 
diminished  to  about  -fa  of  an  inch. 
At  about  this  point  the  cartilage 
rings  disappear,  but  the  tubes  still 
divide  until  the  smallest  are  only  -fa 
of  an  inch  in  diameter.  At  the  very 
ends  of  the  smallest  tubes,  there  is 
an  enlargement  about  -fa  of  an  inch 
in  diameter,  called  a  pulmonary  lobule 
(Fig.  37).  It  constitutes  a  small  cav- 
ity, into  which  dip  little  partitions,  that  do  not  meet 
each  other,  but  create  minute  hollow  spaces  around 
the  sides  of  the  lobule,  called  pulmonary 
vesicles.  These  are  about  fa  of  an  inch 
in  diameter,  and  are  the  smallest  divis- 
ions of  the  lung. 

134.  The  Lining  Membrane  of  the 
Lungs. — All  these  tubes  and  passages, 
down  to  the  most  minute,  are  lined 
with  a  delicate  mucous  membrane, 
which  has  this  remarkable  peculiarity. 
The  little  epithelial  cells  with  which  all 
mucous  membranes  are  covered,  have 
in  this  situation  what  are  called  cilia  at 
their  ends  (Fig.  38).  That  is  to  say, 
each  cell  has  at  its  tip  a  fine,  hair-like 
lash,  which  keeps  in  constant  motion, 
as  the   person   lives,  and    for   some   time 


Fig.  38.— Cilia- 
ted epithelium 
from  a  small 
bronchial  tube. 
The  small 

round  cells  at 
the  bottom  are 
young  ones. 


as 


long 


104  ORGANS  OF  REPAIR. 

after  he  is  dead.  If  a  piece  of  the  mucous  mem- 
brane from  a  frog's  throat  be  snipped  off  with  a 
pair  of  scissors,  and  then  doubled  with  the  natu- 
rally outer  side  outward,  and  placed  under  the  mi- 
croscope, this  incessant  motion  of  the  cilia  may  be 
easily  seen.  It  is  an  experiment  well  worth  trying, 
for  it  is  an  astonishing  and  beautiful  sight  even  to 
one  who  has  often  seen  it.  The  cilia,  although 
they  are  so  delicate  in  their  structure,  are  so  in- 
numerable and  act  in  such  perfect  concert,  that 
they  keep  up  a  constant  current  toward  the  outside 
of  the  body.  They  probably  aid  in  the  expulsion 
of  the  foul  gases  which  the  blood  leaves  in  the 
lungs. 

135.  Asthma.  —  The  smaller  bronchial  tubes, 
which  have  no  rings  of  cartilage,  are  nevertheless 
surrounded  by  involuntary  muscular  fibers.  When, 
in  consequence  of  disease,  these  fibers  contract 
strongly,  they  diminish  the  caliber  of  the  tubes,  and 
render  it  very  difficult  sometimes  for  the  sufferer 
to  get  air  through  them  in  either  direction.  This 
condition  gives  rise  to  great  distress  and  a  sense 
of  suffocation,  and  is  called  astlima. 

136.  The  Blood- Vessels  of  the  Lungs. — Between 
the  pulmonary  vesicles  run  the  small  blood-vessels 
immediately  under  the  delicate  mucous  membrane, 
so  that  the  blood  comes  almost  in  contact  with  the 
air  that  we  breathe.  They  surround  the  vesicles 
completely,  and  it  is  in  this  part  of  the  lung  that 
the  great  changes  take  place  in  the  blood  during 
respiration. 

137.  The  Outer  Covering  of  the  Lungs. — The 
outside  of  the  lung  is  covered  by  serous  membrane, 
and  so  is  the  inside  of  the  chest-wall.     This  renders 


RESPIRATION. 


105 


the  movements  of  the  lung  painless  and  easy.  This 
membrane  is  called  the  pleura,  and  when  it  becomes 
inflamed,  in  the  disease  known  as  pleurisy,  respira- 
tion becomes  excessively  painful. 

138.  Inspiration. — As  the  cavity  of  the  chest  is 
enlarged,  the  air  already  in  the  lungs  is  rarefied, 
and  the  external  atmospheric  pressure  forces  air 
in  to  fill  the  organs.  We  have  already  stated  that 
the  ribs  are  so  shaped,  and  so  connected  with  the 
spine  behind  and  the  sternum  in  front,  that  when 
they  are  raised  up  toward  the  shoulders  the  sides 
move  outward,  and  the  sternum  moves  forward. 
This  motion  of  the  ribs  is  caused  partly  by  power- 
ful muscles  attached  to 
their  external  surface  all 
the  way  down  the  chest, 
and  partly  by  short  mus- 
cles which  pass  between 
the  ribs  from  the  lower 
edge  of  each  one  to  the 
upper  edge  of  the  one 
just  below  it. 

But,  in  addition  to  its 
expansion  toward  the 
front  and  sides,  the  cav- 
ity of  the  chest  is  en- 
larged in  a  downward 
direction  by  the  con- 
traction of  the  diaphragm 
(Fig.  39).  This  muscle 
has  a  strong,  flat,  ten- 
dinous center,  from  every  side  of  which 
muscular  fibers  pass  to  the  walls  of  the  chest.  It 
separates  the  chest  from  the  abdomen,  and  while 


Fig.  39. — Diagram  illustrating  the  vary- 
ing position  of  the  diaphragm  during 
respiration. 


strong 


I06  ORGANS  OF  REPAIR. 

the  muscular  portion  of  it  is  attached  to  the  lower 
ribs,  the  spine  and  the  very  end  of  the  breastbone, 
the  center  rises  much  higher  in  the  chest,  so  that 
it  has  the  shape  of  a  vaulted  roof,  on  top  of  which 
are  the  lungs  and  heart,  and  underneath  the  stom- 
ach and  liver.  Of  course  there  are  passages  through 
it  for  the  blood-vessels  and  nerves,  but  these  open- 
ings are  so  guarded  that  the  diaphragm  forms  a 
tight  partition.  Now,  as  the  center  of  the  diaphram 
rises  so  much  higher  than  the  sides,  it  is  very  evi- 
dent that  a  contraction  of  the  muscular  fibers  will 
pull  the  center  downward,  and  so  increase  the  ca- 
pacity of  the  chest.  And  this  is  what  actually 
occurs  at  every  inspiration.  When  this  contrac- 
tion takes  place  spasmodically,  the  air  is  drawn 
into  the  lungs  with  a  sudden  impulse,  and  we  call 
it  hiccough* 

139.  Expiration.  —  Inspiration  then  involves  a 
contraction  of  many  muscles,  and  they  act  with  a 
great  deal  of  force,  for  they  have  to  lift  the  atmos- 
phere, which  is  pressing  on  the  outside  of  the 
chest  with  a  force  of  fifteen  pounds  to  the  square 
inch.  By  this  simultaneous  contraction,  the  ribs 
are  drawn  out  of  their  natural  position — i.  e.,  they 
are  drawn  upward  into  a  position  which  they  never 
would  assume  if  left  to  themselves.  By  the  elastici- 
ty of  their  cartilages  and  other  tissues  attached  to 
them,  they  tend  to  return  to  their  former  position 
as  soon  as  the  force  which  has  drawn  them  out  of 

*  Hiccough,  being  due  to  a  spasmodic  action  of  the  diaphragm,  may 
be  stopped  by  any  means  that  tends  to  control  the  spasm.  The  easiest 
method  is  to  put  the  diaphragm  on  the  stretch,  as  follows  :  prolong  the 
act  of  expiration  as  much  as  possible,  and  at  the  end  make  a  forcible 
expiration ;  then  inspire  slowly  and  take  as  full  an  inspiration  as  pos- 
sible.    It  is  rare  that  a  second  trial  will  be  necessary. 


RESPTRATIOX. 


107 


it  ceases.  The  diaphragm,  also,  when  contraction 
stops,  tends  to  recover  its  former  arched  shape. 
The  lungs  also  contain,  in  addition  to  the  elements 
already  mentioned,  a  large  amount  of  elastic  fibers, 
interlaced  with  the  other  tissues  in  every  direction. 
These,  too,  as  soon  as  the  pressure  which  has 
stretched  them  ceases,  tend  to  return  to  their  for- 
mer condition.  This  elasticity  of  the  different 
organs  concerned  in  the  act  of  respiration,  then, 
brings  the  chest  and  lungs  back  to  the  condition  in 
which  they  were  before  inspiration  began.  This 
is  the  ordinary  act  of  expiration. 

140.  Relative  Force  of  Inspiration  and  Expira- 
tion.— As  we  usually  breathe,  then,  the  act  of  inspi- 
ration is  an  active  one,  requiring  effort  and  power- 
ful muscular  contraction,  while  the  act  of  expira- 
tion is  passive,  and  is  accomplished  by  the  elasticity 
of  the  tissues." 

Under  other  conditions,  however,  the  act  of 
expiration  may  be  more  powerful  than  that  of  in- 
spiration. There  are  strong  muscles  connected 
with  the  chest  in  such  a  way  as  to  act  in  opposition 
to  the  muscles  of  inspiration,  and  make  the  cavity 
of  the  chest  smaller  than  it  ordinarily  is.  It  is  by 
the  active  contraction  of  these  muscles  that  we  pro- 
duce what  is  called  a  forced  expiration,  which  has 
been  estimated  by  careful  observers  to  be  one  third 
more  powerful  than  a  forced  inspiration. 

141.  Amount  of  Air  respired  with  Each  Breath. 

*  The  outer  surface  of  the  lungs  is  kept  in  contact  with  the  chest- 
walls  by  atmospheric  pressure.  If  the  chest-wall  be  punctured,  so 
that  the  air-pressure  is  the  same  both  outside  and  inside  of  the  lung, 
the  elasticity  of  the  organ  is  such  that  it  immediately  collapses,  driving 
out  all  the  air  from  its  interior. 


108  ORG  AX S  OF  REPAIR. 

— The  amount  of  air  taken  into  the  lungs  with  each 
inspiration  is  about  twenty  cubic  indies.  Now,  the 
entire  capacity  of  the  lungs  varies  in  different  per- 
sons from  one  hundred  and  fifty  to  two  hundred 
and  fifty  cubic  inches  or  even  more.  So  that  with 
each  breath,  a  very  small  amount,  generally  not 
one  tenth,  of  the  air  in  the  lungs  is  changed.  It  is 
even  estimated  that  after  the  most  forcible  expira- 
tion possible,  at  least  one  hundred  cubic  inches  of 
air  will  remain  in  the  chest  of  a  man  of  medium 
size,  which  can  not  be  expelled.  In  ordinary  breath- 
ing, therefore,  only  the  air  in  the  larger  bronchial 
tubes  can  pass  in  and  out  of  the  lungs.  But  the 
changes  in  the  blood  must -be  produced  at  the  ex- 
treme end  of  the  finest  tubes  in  the  pulmonary 
vesicles.  So  the  question  arises,  How  does  the  air 
get  to  the  vesicles  ? 

142.  How  the  Air  in  the  Lungs  is  changed. — In 
the  first  place,  the  law  of  the  diffusion  of  gases  comes 
in  play.  When  two  gases  come  together,  they  tend 
to  mingle  with  each  other  until  they  finally  occupy 
equally  the  whole  of  the  vessel  or  other  confined 
space  in  which  they  may  be.  After  the  mixture, 
each  gas  will  be  found  in  the  same  proportion  in 
every  part  of  the  vessel.  Xow,  the  air  in  the  pul- 
monary vesicles  and  smallest  bronchial  tubes  is 
heavily  loaded  with  carbon  dioxide  (carbonic  acid), 
while  that  which  is  drawn  in  with  inspiration  is  rich 
in  oxygen.  These  two  gases,  then,  carbon  dioxide 
and  oxygen,  are  constantly  being  diffused  through- 
out the  whole  of  the  lungs.  In  the  second  place, 
the  cilia,  which  have  already  been  described,  being 
in  constant  motion,  keep  up  a  current  of  the  foul 
air  from  the   pulmonary  vesicles  along  toward  the 


~> 


RESPIRA  TIOX.  1 09 

larger  bronchi  and  trachea,  and  fresher  air  keeps 
constantly  pressing  in  to  fill  the  place  of  what  has 
been  in  this  way  removed.  Thus,  in  the  smallest 
bronchial  tubes,  there  are  always  two  currents  of  air 
passing  each  other  in  opposite  directions  :  one,  im- 
mediately next  the  mucous  membrane,  being  a  thin 
layer  moving  outward ;  and  the  other,  in  the  center 
of  the  tube,  moving  inward  (Fig.  40).  So  that  the 
air  in  the  larger  bronchi  and  trachea  is  changed 
periodically  by  the  acts  of 
inspiration  and  expiration, 
while  the  circulation  of 
the  air  in  the  small  bron- 
chial tubes  and  pulmonary  Fig.  40.— Imaginary  section  of  a 
Vesicles  is  COntinuOUS.  smaU  bronchial  tube,   showing 

.  r  a  •  *-ke  influence  of  the  cilia  in  pro- 

143.    Amount  01  Air  re-  ducing  an  outward  current  of  air. 

spired  daily. — The  amount 

of  air  taken  in  with  every  inspiration  is  about  twen- 
ty cubic  inches.  The  average  number  of  respira- 
tions per  minute  is  eighteen.  This  is  a  matter 
which  varies  very  much  with  the  individual.  Chil- 
dren and  women  breathe  somewhat  more  rapid- 
lv  than  men  ;  but  taking  eighteen  as  the  average, 
the  quantity  of  air  breathed  per  minute  is  three  hun- 
dred and  sixty  cubic  inches,  or  about  one  fifth  of  a 
cubic  foot.  In  an  hour,  then,  we  use  about  twelve 
cubic  feet  of  air,  and  in  a  day  nearly  three  hun- 
dred  cubic  feet.  This  amount  is  increased  by  every 
muscular  exertion,  and  also  by  the  curious  fact  that 
the  ordinary  respiration  does  not  seem  to  be  alto- 
gether sufficient  for  the  needs  of  the  body,  and  every 
now  and  then  we  draw  a  deeper  breath  than  the 
average.  This  occurs  usually  about  once  in  every 
five  or  six  acts  of  respiration.  Considering  the  in- 
6 


HO  ORGANS  OF  REPAIR. 

crease  in  the  amount  of  air  respired  at  each  long* 
breath,  and  the  increase  of  rapidity  of  respiration 
due  to  slight  causes  during  the  day,  it  is  estimated 
that  an  adult  really  respires  about  three  hundred 
and  fifty  cubic  feet  of  air  per  day. 

144.  Changes  produced  in  the  Air  by  Respira- 
tion.— When  the  air  enters  the  lungs  it  contains 
nearly  21  per  cent  of  oxygen  and  79  per  cent  of  nv 
trogen,  with  about  one  twentieth  of  one  per  cent  of 
carbon  dioxide,  a  little  zvatery  vapor,  and  a  trace  of 
ammonia. 

If  the  air  be  collected  at  expiration,  after  having 
undergone  the  changes  in  the  lungs,  we  find  the 
following : 

1.  //  has  lost  oxygen. 

2.  It  Jias  gained  carbon  dioxide. 

3.  It  contains  more  zvatery  vapor. 

The  watery  vapor  in  the  expired  air  is  not  or- 
dinarily visible,  but  in  cold  weather,  when  it  be- 
comes condensed,  it  can  be  very  plainly  seen.  The 
whole  amount  of  water  passed  away  daily  in  the 
breath  of  a  man  has  been  carefully  estimated,  and 
found  to  average  about  one  and  one  sixth  pound 
avoirdupois. 

145.  Former  Theory  about  the  Formation  of 
Carbon  Dioxide. — Out  of  the  four  cubic  inches  of 
oxygen  taken  into  the  lungs  with  each  inspira- 
tion, one  cubic  inch  disappears.  The  carbon  dioxide 
which  is  exhaled  from  the  lungs  consists  of  carbon 
and  oxygen  united  in  certain  proportions,  and  it 
used  to  be  supposed  that  the  carbon  in  the  blood 
united  with  the  oxygen  of  the  air  in  the  lungs 
themselves,  forming  carbon  dioxide,  and  that  in 
this  way  the  carbon,  released  by  the  wear  and  tear 


RESPIRATION.  Ill 

of  the  body,  was  got  rid  of.  Now,  the  process  of 
combustion  in  a  flame  of  any  kind  consists  in  this 
same  change,  viz.,  the  union  of  the  carbon  and- hy- 
drogen of  the  oil  or  other  inflammable  substance 
with  the  oxygen  of  the  surrounding  air,  forming 
carbon  dioxide  and  water,  and  giving  out  heat 
during  the  process.  So  it  was  for  a  long  time 
thought  that  the  lungs  were  a  sort  of  furnace  in  the 
body,  where  the  carbon  and  hydrogen  of  the  blood 
were  burned,  so  to  speak,  and  the  products  of  com- 
bustion exhaled,  while  the  heat  occasioned  by  the 
process  kept  up  the  warmth  of  the  body.  This  was 
a  beautiful  theory,  but  it  is  found  not  to  be  warrant- 
ed by  the  facts. 

There  is  more  oxyge?i  absorbed  in  the  lungs,  with 
every  respiration,  than  is  exhaled  in  the  carbon  di- 
oxide and  watery  vapor  taken  together.  This  fact 
of  itself  disproves  the  above  theory,  for  it  shows 
that  a  portion  of  the  oxygen  disappears  in  the 
lungfs,  or  is  carried  away  by  the  blood. 

146.  Organic  Matter  in  the  Breath.  —  Besides 
the  carbon  dioxide  given  off  in  the  expired  air, 
there  is  a  certain  amount  of  organic  matter,  con- 
taining nitrogen,  which  gives  the  breath  a  slight 
but  peculiar  odor.  Where  many  persons  are 
breathing  in  a  badly  ventilated  room,  this  organic 
matter  accumulates,  and  imparts  to  the  atmosphere 
that  odor  which  we  all  recognize  as  peculiarly  op- 
pressive and  close. 

147.  Changes  in  the  Blood  during  Respiration. 
— The  blood  undergoes  changes  in  its  passage 
through  the  lungs  which  correspond  to  the  changes 
in  the  air.  In  the  first  place,  it  is  altered  in  its 
color.     As  it  enters  the  lungs,  it  is  of  a  deep  bluish 


112  ORGANS  OF  REPAIR. 

purple,  almost  black ;  as  it  emerges,  it  is  of  a  beau- 
tiful and  most  brilliant  scarlet.  On  chemical  ex- 
amination, to  determine  the  cause  of  this  remark- 
able change,  it  is  found  that  the  blood  which  comes 
away  from  the  lungs  contains  more  oxygen  and 
less  carbon  dioxide  than  that  which  enters  them. 
Additional  proofs  that  the  formation  of  carbon  di- 
oxide does  not  take  place  by  direct  combination 
in  the  lungs  are  the  facts  that  the  venous  blood, 
before  it  enters  the  lungs,  is  deeply  charged  with 
carbon  dioxide  already  formed,  and  that  the  blood 
which  comes  away  from  the  lungs  contains  oxygen 
in  free  solution. 

The  brilliant  color,  which  is  the  result  of  this 
change  in  the  blood,  has  not  yet  been  satisfactorily 
accounted  for.  It  has  been  proved  that  the  oxy- 
gen and  carbon  dioxide  are  carried  by  the  blood- 
corpuscles,  and  not  by  the  plasma,  and  the  change 
of  color  in  the  blood  is  entirely  due  to  the  change 
in  those  minute  bodies.  They  have  been  said  to 
change  their  shape  and  become  more  globular  in 
one  case  than  in  the  other,  but  the  attempts  to  ex- 
plain the  difference  of  color  have  not  yet  been  en- 
tirely successful.* 

148.  Where  the  Carbon  Dioxide  is  formed. — If 
the  carbon  dioxide  is  not  formed  in  the  lungs, 
then  where  does  it  come  from  ?  Experiments  of 
the  most  ingenious  kind  have  been  performed  to 
determine  this  question,  and  they  are  too  long  to 

*  The  coloring-matter  of  the  red  corpuscles  is  called  hcemoglobin. 
It  is  found  that  this  substance,  when  united  with  an  excess  of  oxygen, 
forming  oxyhemoglobin,  has  a  bright  scarlet  color,  and,  when  the 
amount  of  oxygen  is  greatly  reduced,  is  of  a  dark  purple.  But  this 
does  not  explain  much. 


RESPIRA  TION. 


"3 


mention  in  detail.  But  it  has  been  conclusively 
shown  that  most  of  the  carbon  dioxide  is  formed 
in  the  tissues  in  all  parts  of  the  body,  during  the 
processes  of  nutrition.  And  even  here  it  is  not 
produced  by  a  direct  combination  of  the  oxygen 
with  the  carbon,  for  the  exhalation  of  carbon  di- 
oxide will  continue  for  a  considerable  time  in  an 
atmosphere  of  hydrogen,  where  of  course  there  is 
no  oxygen  furnished  to  the  tissues.  The  carbon 
dioxide,  then,  is  formed  by  decomposition  of  the 
tissues,  and  the  oxygen  is  used  by  them  to  build 
themselves  up  again. *  The  amount  of  carbon  di- 
oxide given  off  in  the  breath  has  been  found  to  be 
somewhat  less  than  one  cubic  inch,  or  about  four- 
teen cubic  feet  per  day,  weighing  about  a  pound 
and  a  half,  and  representing  waste  of  the  organism 
to  about  this  amount. 

149.  Composition  of  Air. — Air  being  so  essential 
to  life,  it  is  evidently  important  to  have  it  as  pure 
as  possible.  It  must  contain  enough  oxygen,  so 
that  with  each  respiration  the  temporary  needs  of 
the  body  may  be  satisfied,  and  should  contain  no 
substances  which  are  injurious  to  life  or  health. 
Now,  the  air  normally  contains  about  four  parts 
of  nitrogen  to  one  of  oxygen.  It  always  contains 
a  small  amount  of  carbon  dioxide,  and  a  variable 
quantity  of  watery  vapor.f     It  is  also  never  found 

*  It  will  be  understood  that  the  place  of  the  carbon  which  is  lost  to 
the  body  in  the  carbon  dioxide  which  passes  off  by  the  lungs,  is  sup- 
plied by  the  fresh  material  taken  in  with  the  food. 

f  This  watery  vapor  is  a  very  necessary  constituent  of  the  air.  Out- 
of-doors  the  amount  of  it  is  regulated  in  ways  beyond  our  control  ; 
but  in-doors,  unless  special  care  is  taken,  the  air  may  be  so  dried  by 
artificial  heat,  that  when  respired  it  will  absorb  more  than  the  ordinary 
amount  of  moisture  from  the  mucous  lining  of  the  lungs.     Then  the 


U4 


ORGANS  OF  REPAIR. 


entirely  free  from  impurities,  such  as  other  gases 
than  those  named,  in  small  quantity,  and  minute 
floating  particles  of  matter,  which  we  group  to- 
gether under  the  common  name  of  dust. 

It  has  been  shown,  however,  that  the  breathing 
of  animals  is  continually  removing  oxygen  from  the 
air  and  increasing  the  amount  of  carbon  dioxide. 
Now,  carbon  dioxide  is  a  poison  to  animals,  and 
if  inhaled  in  large  amount  produces  almost  imme- 
diate unconsciousness  and  death.  It  is  for  this  rea- 
son that  it  is  being  constantly  rejected  from  the 
body.  If  this  process  of  removing  oxygen  from 
the  air  and  adding  carbon  dioxide  to  it  were  to 
go  on  indefinitely,  it  is  evident  that  after  a  time 
the  one  would  be  so  much  reduced  in  amount, 
and  the  other  so  much  increased,  that  animals 
would  die  of  carbon-dioxide  poisoning — i.  e.,  of 
asphyxia. 

150.  Respiration  of  Plants.  —  This  danger  is 
guarded  against  in  the  outer  atmosphere  by  the 
constant  absorption  of  carbon  dioxide  by  plants. 
All  plants,  through  their  leaves,  decompose  car- 
bon dioxide  into  its  original  parts,  carbon  and 
oxygen.  The  carbon  they  appropriate  for  their  own 
nourishment,  and  the  oxygen  they  return  to  the  at- 
mosphere. Thus  the  respiration  of  plants  is  exactly 
the  reverse  of  that  of  animals.  The  latter  absorb 
oxygen  and  give  out  carbon  dioxide,  and  the  for- 
mer absorb  carbon  dioxide  and  give  out  oxygen. 

mucous  membrane  becomes  dry,  there  is  an  increased  flow  of  blood  to 
the  part,  and,  if  the  dryness  of  the  air  is  not  remedied,  inflammation 
may  result — i.  e.,  a  catarrh.  For  this  reason  a  vessel  of  water  should 
always  be  kept  on  the  top  of  a  heated  stove  or  furnace,  that  its  evapo- 
ration may  insure  sufficient  moisture  in  the  air  to  prevent  injury  to  the 
lungs  and  throat. 


RESPIRATION.  115 

By  this  never-ending  interchange  the  proportions 
of  oxygen  and  carbon  dioxide  in  the  atmosphere 
are  kept  about  the  same. 

151.  Contamination  of  the  Air  in  Houses. — In- 
doors, however,  there  is  no  opportunity  for  this 
self-purification.  Even  if  a  few  plants  are  kept  in 
the  house,  the  amount  of  carbon  dioxide  they  con- 
sume is  very  little,  and  the  effect  they  are  able  to 
produce  toward  purifying  the  room  can  not  be  com- 
pared with  that  of  the  immense  stretches  of  forest 
and  plain  out-of-doors.  Moreover,  the  amount  of 
carbon  dioxide  in  houses  is  increased  by  combus- 
tion. A  five-foot  gas-burner  throws  out  as  much 
carbon  dioxide  as  five  men.  The  unhealthiness  of 
a  closed  room  is  also  increased  by  the  organic  mat- 
ter of  the  breath,  which  is  very  poisonous.*  The 
odor  of  this  matter  is  perceptible  in  a  room  long 
before  the  accumulation  of  carbon  dioxide  reaches 
a  point  when  it  is  likely  to  be  injurious.  It  is,  there- 
fore, to  be  looked  upon  as  by  far  the  most  danger- 
ous impurity  in  the  atmosphere  of  an  occupied 
room. 

152.  Ventilation. — In  order  to  forestall  any  evil 
result  from  such  impurities,  the  air  of  a  room  should 
be  changed  frequently  enough  to  prevent  the  odor 
of  this  organic  matter  from  being  perceptible.  This 
usually  requires  some  special  attention,  and  is  called 
ventilation.  In  warm  weather,  all  that  is  necessary 
is  to  open  the  doors  and  windows  and  allow  the  air 
to  circulate  freely  through  the  house.     But  in  cold 

*  The  composition  of  this  organic  matter  is  not  known.  It  is  given 
off  in  such  small  quantity  that  the  chemists  have  never  been  able  to 
analyze  it.  It  putrefies  rapidly  after  it  has  left  the  body,  and  then  be- 
comes very  offensive. 


Il6  ORGANS  OF  REPAIR. 

weather  more  care  is  required.  A  fireplace,  with 
an  open  fire,  is  an  excellent  means  of  drawing  out 
the  foul  air — sending  it  up  the  chimney,  and  so  out 
of  the  house.  The  fresh  air,  to  supply  the  place  of 
what  has  been  thus  removed,  may  come  in  through 
cracks  in  the  windows  and  doors.  But  the  fresh 
air  admitted  in  this  way  in  cold  weather,  being 
heavier  than  warm  air,  falls  and  sweeps  along  the 
floor.  This  is  very  dangerous,  for  few  people 
can  endure  a  cold  draught  on  the  feet  and  ankles, 
while  the  rest  of  the  body  is  warm,  without  tak- 
ing cold.  Moreover,  the  smallness  of  the  apertures 
through  which  the  air  comes  increases  the  ra- 
pidity of  the  current.  It  is  better,  therefore,  to  let 
in  the  fresh  air  through  a  special  opening,  so  ar- 
ranged that  the  cold  air  shall  not  immediately  fall 
to  the  floor.  This  can  be  done  cheaply  and  effect- 
ively by  raising  the  lower  sash  of  the  window  about 
four  inches,  and  putting  underneath  it  a  board,  fit- 
ted to  close  the  opening  tightly  between  the  sash 
and  the  sill.  There  will  then  be  a  long,  narrow 
opening  between  the  upper  and  lower  sash,  through 
which  air  will  enter  in  a  current  directed  upward 
toward  the  ceiling,  and,  before  it  descends,  its  mo- 
mentum will  be  so  much  diminished  that  it  will  not 
create  a  draught.  In  very  cold  places,  where  double 
windows  are  used,  the  same  result  may  be  obtained 
by  raising  the  lower  outer  sash  a  little,  and  lowering 
the  upper  inner  one.  The  best  way,  however,  is  to 
warm  the  fresh  air  before  it  enters  the  room ;  but 
this  is  too  large  a  subject  for  discussion  here. 

This  foul  organic  matter  from  the  lungs  of  ani- 
mals, when  it  gets  out  into  the  open  air,  is  im- 
mensely diluted,  and,  being  acted  upon  by  the  oxy- 


RESPIRATION. 


11/ 


gen  of  the  atmosphere,  is  changed  into  other  and 
less  harmful  substances,  which,  in  their  turn,  are 
washed  down  by  the  rain  and  become  a  part  of  the 
soil. 

153.  Contagious  Diseases.  —  The  air  is  not  only 
polluted  by  these  products  of  the  respiration  of 
healthy  animals,  but  it  is  made  unfit  for  breathing, 
in  a  way  involving  still  more  danger  to  life,  by 
the  matters  given  off  from  the  lungs  and  bodies  of 
sick  persons.  There  are  certain  diseases  which  are 
called  contagious  or  infectious,  because  they  can  be 
communicated  from  one  person  to  another.  Such 
diseases  are  small-pox,  measles,  scarlet  fever,  typhus 
fever,  diphtheria,  and  perhaps  consumption.*  It  is 
known  that  the  matters  contained  in  the  air  expired 
from  the  lungs,  or,  in  some  cases,  specks  of  matter 
cast  off  from  the  skins,  of  persons  sick  with  these 
diseases,  will  produce  similar  diseases  in  persons 
who  inhale  them.  Exactly  what  it  is  that  repro- 
duces the  disease  is  not  known,  but  there  is  believed 
to  be  a  microscopic  organism,  peculiar  to  each  dis- 
ease, which,  like  a  kind  of  seed,  will  always  produce 
that  disease  by  its  own  growth  and  multiplication 
whenever  it  meets  with  proper  conditions.  Whether 
these  little  organisms  ever  grow  and  multiply  out- 
side of  the  body  we  do  not  know,  but  that  they  do 
so  in  the  blood  we  have  abundant  evidence.f 

*  Whooping-cough,  mumps,  and  chicken-pox,  are  propagated  in  a 
similar  manner,  but  are  less  dangerous. 

f  It  is  thought  by  some  that  malarial  fevers  (fever-and-ague,  etc.)  are 
produced  by  microscopic  organisms  of  this  kind,  but  this  is  uncertain. 
It  is  well  for  those  who  live  in  districts  where  such  diseases  are  preva- 
lent to  remember  that  the  poison,  whatever  it  may  be,  is  most  active  in 
the  spring  and  fall,  at  night,  and  near  the  surface  of  the  ground.  In 
such  a  region,  and  at  such  a  season,  therefore,  people  should  not  go 


n8  ORGANS  OF  REPAIR. 

There  are  other  diseases  which  are  believed  to 
be  produced  by  similar  organisms  growing  and  mul- 
tiplying in  the  discharges  from  the  stomach  and 
bowels.  Such  organisms  are  believed  to  grow  out- 
side the  body  as  well  as  inside,  and  are  supposed  to 
be  the  cause  of  Asiatic  cholera,  typhoid  fever,  and 
yellow  fever.* 

154.  Precautions  against  such  Diseases.  —  It  is 
probable  that  all  of  these  microscopic  organisms 
(called  bacteria,  bacilli,  micrococci,  etc.)  which  float 
about  in  the  atmosphere,  if  they  do  not  find  a  favor- 
able place  in  some  animal  body,  where  they  can 
grow  and  propagate  their  kind,  finally  die.  If  it 
were  not  so,  the  human  race  would  be  exterminated 
by  them.  But  men  have  two  ways  of  dealing  with 
them  so  as  to  prevent  their  spreading.  One  is  to 
separate  the  sick  person  from  well  ones,  as  far  as 
possible,  and  the  other  is  to  kill  these  little  organ- 
isms as  fast  as  they  leave  the  body  and  before  they 
can  get  out  of  the  room.  This  is  accomplished  by 
the  use  of  powerful  drugs,  called  disinfectants. 

Nurses  and  doctors  adopt  special  means  of  ward- 
ing off  infection,  or  are  willing  to  expose  themselves 

out  after  sundown,  should  keep  their  bedroom-windows  closed,  and 
should  sleep  above  the  first  story. 

*  The  discharges  from  the  bowels  and  kidneys  of  healthy  persons, 
even,  are  believed  to  become  dangerous  when  they  decompose,  and  to 
cause  serious  diseases.  Microscopic  organisms  multiply  in  them  with 
great  rapidity,  and  are  disseminated  in  the  surrounding  atmosphere. 
For  this  reason,  it  is  desirable  that  such  matters  should  be  removed 
from  the  vicinity  of  dwellings  as  quickly  as  possible.  When  they  are 
discharged  into  sewers,  their  decomposition  produces  various  gases- 
some  of  them  very  offensive — which  are  popularly  known  as  sewer-gas, 
but  should  more  properly  be  called,  collectively,  sewer-air.  The  most 
dangerous  thing  about  sewer-air,  however,  is  not  the  offensive  gases, 
but  the  little  organisms  that  float  out  with  it  into  the  streets  or  houses. 


RESPIRATION. 


II9 


to  the  risk  necessary  for  the  proper  care  of  the  sick. 
If  it  becomes  the  duty  of  any  other  person  to  enter- 
a  sick-room,  he  should  have  in  mind  the  following- 
points  :  that  the  nose,  on  account  of  its  narrow  pas- 
sages and  extensive  moist  surface  of  mucous  mem- 
brane, acts  as  a  sort  of  filter,  so  that  many  impurities 
of  the  air  are  detained  there  and  never  reach  the 
lungs,  whereas,  through  the  mouth,  there  is  a  straight 
and  almost  unimpeded  course  to  those  organs ;  that 
the  body  is  less  able  to  resist  injurious  influences  of 
every  kind  when  it  is  fatigued  or  in  want  of  a  fresh 
supply  of  food ;  and  that  matters  escaping  from  the 
bodies  of  the  sick  and  floating  in  the  air  are  likely 
to  settle  on  articles  standing  in  the  room.  Hence 
we  deduce  the  following  rules  : 

Never  enter  a  sick-room  when  you  are  hungry  or 
tired. 

Always  keep  your  mouth  shut,  except  when  talking. 

Never  eat  or  drink  anything  that  has  been  standing 
in  the  sick-room. 


CHAPTER  VII. 

ASPHYXIA. 

155.  Asphyxia. — When  the  blood  is  deprived  of 
its  constant  fresh  supply  of  oxygen,  the  carbon 
dioxide  produced  in  the  tissues  accumulates  very 
rapidly,  and  in  a  short  time  the  blood  is  brought 
into  a  condition  in  which  it  can  not  circulate,  pro- 
ducing asphyxia  or  suffocation.  The  blood  through- 
out the  whole  body  then  becomes  venous.  The 
arteries*  as  well  as  the  veins  are  filled  with  black, 
sluggishly -moving  blood.  This  black  blood  shows 
through  the  skin,  particularly  where  it  is  very  thin, 
as  in  the  lips ;  and  parts  of  the  body  which  are  usu- 
ally of  a  healthy  red  or  pink  color  become  blue  and 
livid.  This  blueness  of  the  lips  and  of  the  flesh  un- 
der the  finger-nails  is,  therefore,  a  sure  indication 
that  the  person  is  suffering  from  a  lack  of  oxygen, 
and  the  only  thing  to  do  to  save  life,  under  such  cir- 
cumstances, is  to  supply  fresh  air.  In  drowning, 
strangling,  poisoning  by  coal-gas  or  illuminating 
gas,  this  is  always  the  great  thing  to  be  aimed  at, 
and,  as  long  as  the  heart  beats,  life  exists,  and  con- 
sciousness can  usually  be  restored. 

*  The  arteries  are  those  blood-vessels  that  carry  the  bright  scarlet 
blood,  which  has  received  a  fresh  supply  of  oxygen,  and  the  veins  con- 
vey the  dark  blood,  called  venous,  which  is  loaded  with  carbon  di- 
oxide and  other  waste  matters,  as  hereafter  explained. 


ASPHYXIA.  I2i 

156.  Drowning.  —  The  length  of  time  during 
which  a  human  being  may  remain  under  water  and 
still  recover,  under  proper  treatment,  is  not  yet  act- 
ually determined.  Young  persons,  it  is  known,  live 
longer  when  submerged  than  older  ones.  As  a  rule, 
however,  a  person  who  has  been  entirely  submerged 
for  five  minutes  is  dead  beyond  the  possibility  of 
resuscitation.  And  yet,  even  in  such  cases,  attempts 
should  be  made,  for  any  case  may  be  an  exceptional 
one.* 

157.  Resuscitation  of  the  Drowned. — What,  then, 
are  the  indications  for  the  treatment  of  a  person  who 
is  almost  dead  from  drowning? 

In  the  first  place,  he  has  been  for  some  time  de- 
prived of  oxygen.  It  is  this  which  has  made  him 
unconscious. 

In  the  second  place,  he  has,  probably,  in  his  fran- 
tic efforts  to  breathe,  taken  water  into  his  lungs, 
where  it  stops  up  the  bronchi  and  air-vesicles,  and 
must  be  cleared  out  before  any  air  can  enter. 

In  the  third  place,  he  is  cold,  and  warmth,  of 
itself,  will  do  much  toward  bringing  about  his  re- 
covery. 

In  the  fourth  place,  his  circulation  is  at  a  very 
low  ebb.  The  blood  is  so  charged  with  carbon 
dioxide  that  it  is  sluggish,  and,  possibly,  has  almost 
ceased  to  flow. 

We  must  first,  then,  turn  the  person  on  his  face, 
and  raise  the  lower  part  of  the  body  somewhat,  so 
as  to  let  what  water  there  may  be  in  the  lungs  run 

*  Unconsciousness  sometimes  persists  for  a  long  time  after  a  person 
has  been  removed  into  fresh  air,  when  no  special  attempts  at  resusci- 
tation have  been  made.  It  is  said  that  persons  have  been  restored  by 
artificial  respiration  after  they  have  lain  unconscious  and  apparently 
dead  for  five  hours. 


122  ORGANS  OF   REPAIR. 

out  by  the  force  of  gravity.  This  action  need  oc- 
cupy only  an  instant,  for,  if  there  beany  water  there, 
it  will  immediately  run  out. 

The  person  should  then  be  laid  flat  upon  the  back, 
without  having  the  head  raised,  for  we  want  the 
first  fresh  blood  to  run  to  the  brain,  and  the  heart 
is  acting  so  feebly  that  it  will  be  unable  to  send  it 
there  if  it  has  to  propel  it  up-hill.  The  shoulders 
should  be  raised  a  little  by  a  pillow,  a  folded  coat, 
or  other  padding.  All  the  clothing  should  be  loosened 
about  the  neck,  chest,  and  waist,  so  as  not  to  inter- 
fere at  all  with  the  movements  of  respiration. 

The  wet,  clinging  clothing,  if  convenient,  should  be 
removed  entirely,  as  it  tends  to  keep  up  the  chilliness 
of  the  body.  In  any  event,  some  one  should  attend 
to  the  duty  of  warming  the  body,  by  rubbing  it  with 
warm  flannels,  by  bottles  of  hot  water  to  the  feet, 
etc.,  etc. 

In  addition  to  these  things,  and  chief  of  all,  arti- 
ficial respiration  should  be  kept  up  until  the  patient 
breathes  naturally,  or  until  absolutely  all  hope  is 
lost. 

158.  Artificial  Respiration. — As  the  person  lies 
upon  the  back,  the  arms  are  to  be  grasped  above 
the  elbows  and  brought  upward  above  the  head,  so 
as  to  touch,  or  nearly  so.  The  large  muscles  of  the 
shoulder  are  attached  to  the  Avails  of  the  chest  in 
such  a  manner  that  this  movement  of  the  arms  raises 
the  ribs,  and  expands  the  cavity  of  the  chest  in  very 
much  the  same  way  that  ordinary  respiration  does. 
The  chest  being  thus  expanded,  of  course  air  rushes 
in,  and  inspiration  is  effected.  The  arms  should 
now  be  returned  to  the  sides  of  the  body  and  pressed 
against  the  ribs,  when  the  chest-walls  will  recover 


ASPHYXIA.  123 

their  former  position  by  virtue  of  their  elasticity, 
and  expel  all  the  air  which  had  been  taken  in.  This, 
it  will  be  observed,  is  exactly  the  process  of  natter al 
expiration.  The  rapidity  of  these  movements  should 
approach  as  nearly  as  possible  to  the  rapidity  of 
natural  respiration — i.  e.,  about  sixteen  or  eighteen 
movements  to  the  minute,  and  the  drawing-  up  of  the 
arms  above  the  head  should  occupy  the  usual  time 
of  inspiration.  This  process  should  be  continued 
for  hours,  if  necessary,  and  the  first  sign  of  recov- 
ery will  usually  be  a  slight  change  in  the  color  of 
the  lips  and  finger-nails  to  red  or  pink,  indicating 
that  the  circulation  and  oxygenation  of  the  blood 
have  begun  to  be  more  active. 

159.  Additional  Precautions. — During  the  whole 
process  of  resuscitation  of  a  drowned  person,  care 
should  be  taken  to  keep  the  mouth  and  tJiroat  clear 
of  mucus  and  froth  by  means  of  a  finger  covered 
with  a  towel.  The  tongue  must  also  be  watched.  In 
persons  who  are  almost  dead  and  have  lost  their 
muscular  power,  this  organ  often  slips  backward 
into  the  throat,  and  covers  the  glottis  so  that  no  air 
can  pass  in  or  out.  It  is  necessary,  in  such  cases, 
for  some  person  to  take  hold  of  the  tip  of  the 
tongue  with  a  towel  to  prevent  its  slipping  from  the 
grasp,  and  draw  it  forward  so  as  to  leave  the  pas- 
sage to  the  lungs  clear.* 

As  soon  as  the  person  begins  to  breathe  he  can 
swallow,  and  a  tablespoonful  of  brandy  should  be 
given  him  in  a  quarter  of  a  tumblerful  of  water, 

*  In  all  cases  of  asphyxia,  pure  air  is  of  the  utmost  importance. 
The  sufferer  should  therefore  be  in  a  well-aired  room,  and  whether  in- 
doors or  out  should  never  be  surrounded  by  a  crowd  of  people,  whose 
respiration  will  pollute  the  air  before  it  reaches  the  one  who  needs  it 
most. 


124 


ORGANS  OF  REPAIR. 


dry  clothing  should  be  placed  upon  him,  and  he 
should  be  put  in  a  warm  bed  until  his  recovery  is 
complete. 

The  above  directions  apply  to  all  cases  of  suffo- 
cation, where  there  is  no  other  injury  to  complicate 
the  results  of  the  mere  deprivation  of  air. 


CHAPTER   VIII. 


THE   HEART. 


160.  General  Plan  of  the  Circulation. — The  cir- 
culation of  the  blood  is  brought  about  by  a  compli- 


ten<s 


Fig.  41. — The  heart  and  the  large  blood-vessels  connected  with  it.     The 
greater  part  of  the  left  ventricle  is  hidden  by  the  right  ventricle. 

cated  series  of  tubes  and  channels,  extending  through 
every  portion  of  the  body,  and  all  communicating 


126  ORGANS  OF  REPAIR. 

with  each  other  and  with  a  powerful  muscular  cen- 
tral organ  called  the  heart.  The  tubes  are  called, 
according  to  their  structure,  size,  and  function,  ar- 
teries, veins,  or  capillaries* 

161.  The  Heart. — The  heart  (Fig.  41)  is  a  strong, 
hollow,  muscular  organ,  lying  behind  the  breast- 
bone, with  its  greater  portion  to  the  left  of  it.  It 
is  shaped  somewhat  like  a  cone,  with  both  ends 
rounded,  and  the  larger  end  directed  upward  and 
toward  the  right.  The  lower  end,  or  apex,  is  free 
to  move  in  any  direction,  not  being  attached  to  any- 
thing, while  the  upper  and  larger  end  is  held  in 
place  by  the  large  blood-vessels  which  are  connected 
with  it  and  also  with  the  spinal  column.  The  whole 
organ  is  covered  with  serous  membrane  called  the 
pericardium,  and  lies  in  a  cavity  which  is  also  lined 
with  serous  membrane,  so  that,  like  the  lungs  and 
abdominal  organs,  its  constant  movements  can  go 
on  with  the  slightest  amount  of  friction. 

162.  The  Double  Circulation. — In  order  to  un- 
derstand the  action  of  the  heart,  it  is  necessary 
to  know,  first,  that  there  is  a  double  circulation  go- 
ing on  in  the  body  at  the  same  time.  At  every 
contraction  of  the  heart  a  portion  of  the  blood  is 
thrown  into  the  lungs  and  another  portion  into  the 
remainder  of  the  body ;  and  these  two  portions 
never  mingle  with  each  other.  To  be  more  precise, 
and  follow  a  particular  mass  of  blood  in  its  course 
through  the  body,  we  may  state  it  thus  :  The  blood 
starts,  we  will  say,  from  a  certain  part  of  the  heart ; 
it  goes  directly  to  the  lungs ;  thence  it  returns  to 
the  heart,  but  to  a  different  part  of  the  organ  ;  then 
it  goes  out  of  the  heart  in  the  arteries  to  what  is 

*  See  Frontispiece. 


THE  HEART. 


127 


called  the  general  circulation — i.  e.,  to  all  parts  of 
the  body,  excepting  the  lungs  ;  thence  it  is  collected 
by  the  veins,  and  returns  to  the  heart ;  at  the  next 
contraction  it  goes  to  the  lungs  again,  and  begins 
the  same  process ;  so  that  in  this  way  all  the  blood 
passes  through  the  lungs,  and  all  of  the  blood  visits 
all  parts  of  the  body ;  but  in  doing  this  it  visits  and 
passes  through  the  heart  twice.  In  short,  it  flows — 
1.  From  the  heart  to  the  lungs ;  2.  Back  to  the  heart ;  3. 
To  the  rest  of  the  body;  4.  Back  to  the  heart.  Thus, 
there  are  two  systems  of  circulation :  one,  called  the 
pulmonary  circulation,  from  the  heart  to  the  lungs 
and  back  again ;  the  other,  the  general  circulation, 
from  the  heart  to  the  body  and  back  again. 

163.  The  Two  Sides  of  the  Heart. — This  double 
and  simultaneous  circulation  can  not  be  brought 
about  by  a  heart  containing  but  one  cavity.  And, 
accordingly,  we  find  that  the  heart  is  divided  by  a 
muscular  partition,  running  lengthwise  of  the  organ 
from  front  to  rear,  into  two  parts  of  nearly  equal 
size,  called  the  right  and  left  sides  of  the  heart. 
The  right  side  carries  on  the  pulmonary  circulation, 
and  the  left  the  general  circulation.  So  that  the 
course  of  the  blood  is  as  follows  :  From  the  right  side 
of  the  heart  to  the  lungs  ;  tJience  to  the  left  side  of  the 
heart ;  thence  to  all  parts  of  the  body  ;  t  lie  nee  back  to 
the  right  side  of  the  heart.  If  this  order  of  the  circu- 
lation be  carefully  observed,  it  will  be  seen  that  the 
right  side  of  the  heart  never  contains  anything  but 
dark  or  venous  blood,  and  the  left  side  always  contains 
bright  or  arterial  blood. 

164.  The  Auricles  and  Ventricles. — Each  side  of 
the  heart  is  divided  into  two  cavities,  making  four 
in  the  whole  organ.     These  cavities  are  called  the 


128 


ORGANS  OF  REPAIR. 


auricles  and  ventricles.  The  ventricles  constitute  the 
greater  part  of  the  heart,  and  it  is  in  their  walls  that 
the  greatest  muscular  power  is  located.  The  auri- 
cles are  smaller  cavities,  situated  at  the  upper  ex- 
tremity of  the  organ,  and  their  walls  are  much 
thinner  and  weaker  than  the  walls  of  the  ventricles. 
The  blood  passes  from  the  veins  into  the  auricles, 
from  the  auricles  into  the  ventricles,  and  from  the 
ventricles  it  is  forced  out  into  the  body.  The  course 
of  the  blood,  then,  is  from  the  body  in  general 
through  the  veins  to  the  right  auricle ;  from  the  right 
auricle  to  the  right  ventricle  ;  from  the  right  vejitricle  to 

the  lungs ;  from  the 
lungs  to  the  left  auri- 
cle ;  from  the  left  au- 
ricle to  the  left  ventri- 
cle ;  from  the  left  ven- 
tricle out  to  the  body 
in  general ',  whence  it 
is  collected  by  the 
veins  and  brought 
back  to  the  right  au- 
ricle, to  begin  the 
same  course  again 
(Fig.  42). 

165.  The  Valves 
of  the   Heart.  —  At 
the    mouths    of    the 
veins,     where     they 
empty  into   the    au- 
ricles, there   are    no 
valves,  and  they  are  not  really  needed  at  this  point, 
for  the  auricles  do  not  contract  with  much  force, 
and  as  there  is  always  a  current  in  the  veins  running 


Fig.  42. — Diagram  illustrating  the  course 
of  the  blood  through  the  heart. 


THE  HEART. 


129 


toward  the  heart,  and  as  the  ventricles  lie  below  the 
auricles,  the  blood  naturally  flows  into  the  ventri- 
cles, where  it  meets  with  no  resistance,  rather  than 
backward,  where  it  would  meet  with  considerable, 
having  to  oppose  the  force  of  gravity  and  also 
the  current  in  the  veins.  In  this  manner  the  ven- 
tricles become  filled  with  blood,  and,  when  they 
begin  to  contract,  the  case  is  very  different.  Here 
there  is  an  enormous  pressure  to  overcome.  The 
right  ventricle  must  contract  with  force  sufficient 
to  send  its  contents  into  the  lungs,  pushing  be- 
fore it  the  column  of  blood  already  in  the  ves- 
sels. The  left  ventricle  has  to  contract  with  a 
force  sufficient  to  send  its  contents  to  the  remotest 
parts  of  the  body,  also  pushing  along  the  blood 
which  is  already  in  the  vessels.  On  the  other  hand, 
the  resistance  backward  toward  the  veins  is  not 
nearly  as  great.  The  current  of  blood  in  the  veins 
is  not  strong,  and,  even  supposing  that  the  resistance 
were  equal  in  both  directions,  it  is  plain  that  the  cir- 
culation would  soon  come  to  an  end.  The  ventricle 
in  contracting  would  force  blood  backward  into  the 
auricles  and  veins,  and  forward  into  the  arteries, 
and  then,  when  the  heart  relaxed,  the  blood  would 
flow  back  again  into  the  ventricles  from  both  direc- 
tions. This  danger  is  averted  by  the  introduction 
of  four  sets  of  valves,  one  between  each  auricle  and 
ventricle,  and  one  at  the  opening  from  the  ventricle 
into  the  artery,  through  which  the  blood  passes  dur- 
ing contraction.  The  valves  of  the  heart  are  double 
folds  of  the  serous  membrane  which  lines  all  the 
cavities  of  the  organ,  and  are  stiffened  somewhat 
by  a  few  fibers  which  run  between  the  folds.  All 
of  these  valves  have  three  flaps,  excepting  the  one 


130 


ORGANS  OF  REPAIR. 


which  separates  the  left  auricle  from  the  left  ventri- 
cle, and  this  has  only  two. 

The  valves  are  all  so  constituted  as  to  allow  the 
blood  to  pass  only  in  one  direction.  The  valves  be- 
tween the  auricles  and  ventricles  will  allow  blood 
to  pass  from  the  auricles  into  the  ventricles,  but  not 
from  the  ventricles  back  into  the  auricles  ;  and  the 
valves  at  the  mouths  of  the  arteries  will  allow  blood 
to  pass  from  the  ventricles  into  the  arteries,  but  not 
from  the  arteries  back  into  the  ventricles. 

166.  The  Blood- Vessels  connected  with  the  Heart. 
— The  large  veins,  by  which  all  the  blood  from  the 
general  circulation  is  poured  into  the  right  auricle, 
are  called  the  vence  cavce  (i.  e.,  the  hollow  veins) ;  the 
large  artery,  by  which  the  blood  passes  from  the 
right  ventricle  to  the  lungs,  is  the  pulmonary  artery  ; 
the  large  veins,  by  which  the  blood  returns  from 
the  lungs  and  enters  the  left  auricle,  are  the  pulmo- 
nary veins  ;  and  the  large  artery,  by  which  the  blood 
goes  out  from  the  left  ventricle  to  all  parts  of  the 
body,  is  called  the  aorta. 

167.  The  Circulation  of  the  Blood. — The  blood, 
then,  coming  from  all  parts  of  the  body  in  the  veins, 
enters  through  the  venae  cavas  into  the  right  auri- 
cle ;  when  the  auricle  is  filled,  it  contracts  and  sends 
the  blood  downward  into  the  right  ventricle  ;  when 
the  ventricle  is  filled,  its  walls  contract,  and  the 
blood  passes  into  the  pulmonary  artery,  its  return 
into  the  auricle  being  prevented  by  the  closure  of 
the  valves  between  the  auricle  and  ventricle  ;  the 
blood  then  goes  through  the  lungs,  and  becomes 
changed  into  arterial  blood ;  it  returns  to  the  heart, 
to  the  left  auricle,  and  passes  from  there  into  the 
left  ventricle  ;  the  contraction  of  the  ventricle  then 


THE  HEART. 


13* 


forces  it  into  the  aorta,  its  return  into  the  auricle 
being  prevented  by  the  valves  ;  from  the  aorta  it 
goes  to  all  parts  of  the  body,  to  be  returned  by  the 
veins  to  the  right  side  of  the  heart.  The  valves  at 
the  mouth  of  the  pulmonary  artery  and  the  aorta 
prevent  the  blood  which  has  entered  them  during 
the  heart's  contraction  from  flowing  back  into  the 
cavity  of  the  ventricle  when  it  becomes  relaxed. 

168.  Peculiar  Valves  in  the  Heart. — There  is  one 
peculiarity  connected  with  the  working  of  certain 
valves  in  the  heart  which  is  one  of  the  most  beauti- 
ful examples  of  adaptation  in  the  whole  body.  It 
has  been  shown  that  there  are  no  valves  at  the 
points  where  the  veins  enter  the  auricles,  and  still, 
when  the  auricles  contract,  the  blood  is  not  forced 
backward  in  the  veins  to  any  great  extent,  but  passes 
downward  into  the  ventricles.  Some  of  the  reasons 
for  this  have  already  been  mentioned,  but  there  is 
the  additional  fact  that  the  opening  between  the 
auricle  and  ventricle  on  each  side  is  very  large,  al- 
most as  wide  as  the  auricle  itself.  There  is,  there- 
fore, very  little  resistance,  hardly  any  in  fact,  to  the 
stream  of  blood  passing  from  either  auricle  to  the 
ventricle.  But  this  large  size  of  the  opening  might 
give  rise  to  imperfect  closure  of  the  valves.  The 
valves  are  made  of  thin  sheets  of  membrane,  stiffened 
a  little  by  fibrous  threads,  but  still  very  flexible.  In 
the  pulmonary  artery  and  the  aorta,  the  openings 
from  the  ventricles  are  so  small  that  the  valves  are 
stiff  enough  to  resist  the  backward  pressure  of  the 
blood  and  keep  the  openings  closed.  The  openings 
from  the  auricles  to  the  ventricles,  however,  are  so 
large  that,  if  there  were  no  special  provision  to  pre- 
vent it,  the  valves  would  not  only  be  pressed  back- 


132 


ORGANS  OF  REPAIR. 


ward  toward  the  auricle  when  the  ventricle  con- 
tracted, so  as  to  meet  at  their  edges  and  close  the 
opening",  but,  on  account  of  their  flexibility,  their 
borders  would  be  bent  still  farther  back,  so  as  to 
open  into  the  auricle,  and  allow  a  reflux  of  blood 
into  that  cavity. 

This  difficulty  is  obviated  in  the  following  man- 
ner :  There  are  numerous  fine  but  strong  fibrous 
threads  or  cords  attached  to  the  edges  of  the  valves, 
and  from  that  point  running  downward  to  the  walls 
of  the  ventricle.  These  cords  are  just  long  enough 
to  allow  the  valves  to  close  perfectly,  but  not  pass 
any  farther  back  toward  the  auricle.  But  here  an- 
other difficulty  arises.  If  the  cords  are  long  enough 
to  allow  the  valves  to  close  at  the  beginning  of  the 
contraction  of  the  ventricle  when  the  cavity  is  at 
its  full  size,  then  they  will  be  too  long  when  the 
contraction  is  toward  its  end  and  the  cavity  is  di- 
minished in  size,  and  allow  the  valves  to  be  pressed 


Fig.  43. — Illustrating  the  action  of  the  valves  in  the  right  side  of  the  heart. 


THE  HEART. 


133 


too  far  back.     In  other  words,  to  fulfill  their  object, 
these  cords  must  be  able  to  become  longer  or  short- 


FiG.  44. — Illustrating  the  action  of  the  valves  in  the  right  side  of  the  heart. 


er  according  to  circumstances.  This  is  effected  by 
small  muscular  projections  or  pillars,  which  extend 
from  the  walls  of  each  ventricle  into  its  interior,  and 
to  which  the  cords  are  attached.  When  the  heart 
contracts,  these  little  pillars  contract  at  the  same 
time,  and  make  the  cords  attached  to  the  valves 
shorter  and  shorter  as  the  contraction  proceeds,  just 
in  proportion  as  the  cavity  of  the  ventricle  grows 
smaller  and  smaller.  In  this  way  the  reflux  of  blood 
through  these  large  valves  is  prevented  (Figs.  43, 

44). 

169.  The  Contraction  of  the  Heart. — The  con- 
traction of  the  heart  does  not  run  successively  from 
one  auricle  to  the  corresponding  ventricle,  and  then 
from  the  other  auricle  to  the  other  ventricle,  but  the 
contraction  of  both  sides  of  the  heart  is  simultane- 
7 


134 


ORGANS  OF  REPAIR. 


ous.  It  begins  at  the  auricles  and  extends  down- 
ward until  the  ventricles  are  both  firm  and  hard  and 
reduced  to  their  smallest  possible  size.  The  organ 
then  becomes  relaxed,  and  is  for  an  exceedingly 
short  time  quiet.  During  this  stage  of  relaxation 
the  auricles  are  being  filled  with  blood  from  the 
veins,  and  there  is  also  a  current  running  into  the 
ventricles  from  the  auricles.  During  the  stage  of 
contraction  the  blood  is  being  forced  into  the  circu- 
lation through  the  aorta  and  the  pulmonary  artery. 

170.  The  Sounds  of  the  Heart. — These  alternate 
contractions  and  relaxations  of  the  heart  are  accom- 
panied by  sounds,  which  are  very  audible  to  any  one 
who  applies  his  ear  to  the  region  of  the  heart  in  a 
living  person.  These  sounds  are  two  in  number,  the 
first  being  a  prolonged,  rumbling  sound,  and  the 
second  short  and  sharp.  The  first  sound  is  made 
during  the  time  when  the  heart  is  contracting,  and 
the  second  just  at  the  end  of  the  contraction,  or  be- 
ginning of  relaxation.  The  first  sound  is  supposed 
to  be  produced  partly  by  the  closing  of  the  large 
valves  between  the  auricles  and  ventricles,  which 
occurs  just  at  the  moment  when  this  sound  begins, 
and  partly  by  the  contraction  of  the  muscular  fibers 
of  the  heart.  The  second  sound  is  positively  known 
to  be  produced  by  the  closing  of  the  pulmonary  and 
aortic  valves.  It  is  by  the  variation  in  distinctness 
and  quality  of  these  sounds,  and  the  addition  of 
other  sounds  to  them,  that  physicians  are  enabled  to 
determine  with  wonderful  accuracy  the  condition  of 
the  valves  of  the  heart. 

171.  Rapidity  of  Pulsation  in  Health. — The  con- 
tractions of  the  heart  take  place  with  regularity,  and 
average  in  the  adult  about  seventy  per  minute.     The 


THE  HEART.  135 

rate  is  higher  in  children  and  women  than  in  men, 
and  this  fact  is  probably  connected  with  their  greater 
impressionability.  The  heart-pulsations  appear  to 
be  slower  in  proportion  as  the  individual  is  cool  and 
deliberate  in  his  judgments.  The  pulse  of  Napoleon 
Bonaparte  is  said  to  have  averaged  only  forty-four 
to  the  minute,  and  is  one  of  the  slowest  on  record. 
Sudden  emotions  may  increase  its  rapidity  and  force, 
so  that  a  process,  of  which  Ave  are  usually  uncon- 
scious, becomes  very  perceptible  and  unpleasant,  or, 
on  the  other  hand,  they  may  cause  it  to  stop  for  a 
moment  altogether,  to  skip  a  beat,  as  it  were,  pro- 
ducing the  sensation  of  "fluttering"  at  the  heart. 
Although  the  action  of  the  heart  is  thus  influenced 
by  our  feelings,  it  is  beyond  our  control.  Its  pulsa- 
tions are  ceaseless  and  regular,  until  interrupted  by 
disease  or  death.  But,  notwithstanding  this  general 
fact,  there  are  some  instances  on  record  of  persons 
who  have  been  able  to  affect  the  action  of  the  heart 
by  an  effort  of  the  will.  The  most  remarkable  one 
of  these,  perhaps,  was  a  Colonel  Townsend,  of  Dub- 
lin. This  person,  on  several  occasions,  in  the  pres- 
ence of  medical  men,  lay  down  and  caused  the 
contractions  of  his  heart  to  become  so  faint  as  to 
be  imperceptible.  During  the  experiment  the  cir- 
culation was  so  far  interfered  with  that  he  became 
pallid  and  unconscious.  After  a  half-hour  or  so,  he 
would  gradually  return  to  his  natural  condition. 
As  might  have  been  expected,  he  performed  the  ex- 
periment once  too  often.  He  stopped  the  action  of 
the  heart  for  the  last  time  in  the  same  way  as  he  had 
done  before,  and  it  never  resumed  its  work. 


CHAPTER   IX. 

THE  BLOOD-VESSELS. 

172.  The  Blood-Vessels. — The  heart,  although 
a  very  powerful  organ,  would  not  be  able  to  force 
the  blood  through  the  whole  body,  and  back  to  itself 
again,  without  assistance,  and  this  assistance  is  fur- 
nished by  the  structure  of  the  blood-vessels  them- 
selves. The  blood  leaves  the  heart  by  the  arteries 
and  comes  back  to  it  through  the  veins,  and  these 
two  systems  of  vessels  differ  very  much  in  their 
structure. 

173.  Structure  of  the  Arteries. — The  arteries  are 
tubes,  with  strong  walls,  described  by  anatomists 
as  having  three  layers.  The  innermost  is  a  delicate, 
smooth  membrane  ;  the  middle  one  is  composed  of 
elastic  fibers  and  also  fibers  of  the  non-striated  or 
involuntary  muscular  tissue  ;  the  outer  one  is  made 
up  of  strong  connective  tissue.  Thus  the  walls  of 
the  arteries  are  very  elastic,  and,  if  the  tube  is  dis- 
tended, it  returns  to  its  former  size  as  soon  as  the 
internal  pressure  is  removed. 

174.  The  Pulse. — When  the  heart  contracts,  its 
contents  are  driven  with  great  force  into  the  ar- 
teries, and,  as  the  blood  already  contained  there  re- 
sists somewhat  the  advance  of  the  fresh  supply,  the 
walls   of   the   arteries   are  stretched    to  accommo- 


THE  BLOOD-VESSELS.  137 

date  the  mass  of  blood  which  is  thrown  into  them. 
When  the  heart  relaxes,  and  the  pressure  from  that 
direction  is  removed,  the  elastic  walls  of  the  arteries 
react  upon  their  contents,  and,  if  it  were  not  for  the 
valves,  would  drive  the  blood,  or  a  portion  of  it, 
back  into  the  heart.  At  the  slightest  backward 
pressure,  however,  the  valves  close,  and  the  elas- 
ticitv  of  the  arteries  thus  gives  the  blood  another 
impulse  forward  toward  the  surface  of  the  body. 
The  impulse  given  by  the  heart's  contraction,  to- 
gether with  that  caused  by  the  recovery  of  their 
natural  position  by  the  walls  of  the  arteries,  gives 
rise  to  the  pulse,  which  can  be  felt  at  any  point  in 
the  body  where  an  artery  runs  near  enough  to  the 
surface.  The  common  place  of  feeling  for  it  is  in 
the  wrist,  merely  because  that  is  the  most  conven- 
ient and  accessible ;  but  it  may  also  be  felt  in  the 
ankle,  in  the  neck,  in  the  temple,  or  in  the  upper 
arm. 

175.  The  Capillary  Blood-Vessels  ;  their  Struct- 
ure.— The  large  vessels,  bv  which  the  blood  leaves 
the  heart,  viz.,  the  pulmonary  artery  and  the  aorta, 
divide  and  subdivide  continually,  the  branches 
growing  smaller  and  smaller  as  they  approach 
their  termination,  their  walls  at  the  same  time  un- 
derofoins:  a  change  in  structure.  The  elastic  tissue, 
which  is  so  abundant  in  the  larger  arteries,  grad- 
ually  disappears  as  the  vessels  diminish  in  size,  and 
the  muscular  tissue  becomes  more  prominent,  until 
even  this  finallv  vanishes,  and  the  smallest  blood- 
vessels, called  the  capillaries,  are  composed  of  a 
thin  membrane,  not  divisible  into  layers.  Thus  the 
largest  arteries  are  very  strong  and  very  elastic, 
while  the  smaller  ones  lose  in  elasticity,  but,  from 


138  ORGANS  OF  REPAIR. 

the   amount  of  muscular  tissue    they  contain,  are 
very  contractile. 

176.  Size  of  the  Capillaries. — The  capillaries,  in 
which  the  arteries  finally  end,  are  only  about  the 
-g-y^  of  an  inch  in  diameter — just  large  enough  to 
allow  the  blood-corpuscles  to  pass  through  them, 
so  to  speak,  in  single  file.  Their  number  is  beyond 
computation.  They  are  so  thickly  strewed  in  the 
body  that  the  point  of  a  fine  cambric  needle  can 
not  anywhere  be  inserted  between  them.  As  every 
one  knows,  it  is  impossible  to  find  an  instrument 
with  a  point  so  fine  as  not  to  wound  a  blood-vessel 
if  introduced  through  the  skin.  These  vessels  are 
entirely  indistinguishable  to  the  naked  eye,  and,  be- 
fore the  discovery  of  the  microscope,  it  was  a  great 
problem  for  anatomists  to  explain  how  the  blood 
got  from  the  arteries  into  the  veins,  as  they  could 
find  no  direct  communication. 

177.  The  Veins. — After  passing  through  the  cap- 
illaries, the  blood  enters  the  veins.  These  vessels 
contain  in  their  walls  much  less  muscular  and  elas- 
tic tissue  than  the  arteries,  and  more  connective 
tissue.  The  consequence  of  this  is,  that  the  walls 
of  the  veins  are  flaccid  and  yielding,  and,  if  they  are 
cut  across,  the  sides  fall  together  and  tend  to  close 
the  opening.  If  an  artery,  on  the  other  hand,  be 
cut,  the  tube  remains  open  and  in  a  sense  rigid,  al- 
though, as  will  soon  be  shown,  its  caliber  is  some- 
what diminished.  The  veins,  very  minute  at  first, 
gradually  unite  and  become  larger  and  larger,  until 
finally  all  the  veins  of  the  general  circulation  form 
two  large  vessels,  called  the  vence  cavce,  which  dis- 
charge their  contents  into  the  right  side  of  the 
heart — one  vena  cava  receiving  all  the  blood  from 


THE  BLOOD-VESSELS. 


139 


the  head  and  upper  extremities,  and  the  other  that 
from  the  rest  of  the  body. 

178.  Circulation  of  Blood  in  the  Veins  ;  Influ- 
ence of  Respiration. — The  circulation  of  the  blood  in 
the  veins  is  brought  about  in  three  ways :  In  the  first 
place,  the  act  of  respiration  has  its  influence.  When 
the  chest  is  expanded  by  muscular  action,  every 
fluid  which  is  outside  of  it  tends  to  rush  in  and  fill 
the  enlarged  cavity.  The  chief  space  is  filled  by 
the  air,  as  that  is  more  perfectly  fluid  and  meets 
with  the  least  resistance  from  friction.  But  the 
blood  is  also  drawn  in  through  the  veins,  and  the 
real  extent  and  power  of  this  suction  can  be  very 
easily  seen  whenever  the  entrance  of  air  is  im- 
peded. In  such  cases  the  veins  in  the  neck  can  be 
plainly  seen  to  become  swollen  and  full  during  ex- 
piration, and  emptied  again  during  inspiration. 

179.  Influence  of  Muscular  Contraction. — In  the 
second  place,  the  contraction  of  the  voluntary  mus- 
cles aids  in  the  return  of  the  blood  to  the  heart. 
While  the  arteries,  as  a  rule,  run  deep  in  the  body, 
out  of  the  reach  of  injury,  the  veins  are  largely  near 
the  surface,  and  the  whole  exterior  of  the  body  is 
more  or  less  streaked  by  the  blue  lines  which  indi- 
cate their  course.  Now,  during  the  contraction  of 
a  muscle,  it  not  only  shortens  but  becomes  broader 
and  thicker,  and,  of  course,  compresses  to  a  greater 
or  less  degree  everything  near  it.  Thus  the  veins 
are  continually  being  pressed  upon  here  and  there, 
in  various  parts  of  the  body,  during  the  whole  of 
our  waking  hours,  and  even  to  some  extent  during 
sleep. 

180.  The  Valves  of  the  Veins.  —  But  merely 
pressing  the   blood  out  of  a   certain  portion  of  a 


140 


ORGANS  OF  REPAIR. 


vein  might  send  it  in  either  direction ;  it  would  be 
almost  as  likely  to  send  it  away  from  the  heart  as 
toward  it.  This  reflux  of  blood  in  the  veins  is  pre- 
vented by  valves  (Fig.  45),  which  allow  the  blood  to 
pass  through  them  readily  toward  the  heart,  but 
not  away  from  it.*     These  valves  are  particularly 


Fig.  45. — Diagrams  illustrating  the  action  of  the  valves  in  the  veins. 

numerous  in  the  lower  extremities,  for  here  the 
force  of  gravity  acts  in  opposition  to  the  current  of 
blood,  and  would  seriously  interfere  with  the  circu- 
lation if  there  were  no  special  provision  with  refer- 
ence to  it. 

Thus,  when  blood  has  been  forced  out  of  a  por- 
tion of  a  vein  by  pressure,  it  can  not  go  backward 
on  account  of  the  valves,  but  must  go  forward  in 
every  case.  This  fact  and  the  action  of  the  valves 
may  be  beautifully  seen  in  the  arm  of  any  person, 
where  the  veins  are  not  obscured  by  too  much  fat 
beneath  the  skin.    If  a  place  be  chosen  where  a  vein 

*  It  is  said  that  the  discovery  of  the  proper  working  of  these  valves 
first  suggested  to  William  Harvey  the  true  theory  of  the  circulation  of 
the  blood. 


THE  BLOOD-VESSELS.  141 

is  visible,  with  no  branches  for  an  inch  or  so,  and 
one  finger  be  placed  upon  it  so  as  to  stop  the  flow 
of  blood,  the  portion  of  the  vein  on  the  farther  side 
from  the  heart  will  be  seen  to  fill  with  blood,  and 
at  some  point  will  probably  look  swollen.  This 
slight  swelling  marks  the  situation  of  a  valve.  If 
a  finger  be  passed  along  a  vein  toward  the  heart, 
pressing  upon  it  all  the  time,  the  vein  will  be  seen 
to  fill  behind  the  finger;  while  if  the  finger  be 
passed  in  the  opposite  direction,  away  from  the 
heart,  the  vein  will  be  empty  and  collapsed  behind 
the  finger,  and  perhaps  hardly  noticeable.  This 
clearly  indicates  the  direction  of  the  current  of 
blood. 

181.  Influence  of  the  Pressure  in  the  Capillaries. 
— But  the  third  cause  of  the  venous  circulation,  and 
the  most  important  of  all,  is  the  blood  which  is  con- 
stantly accumulating  in  the  capillaries  and  exercis- 
ing pressure  on  the  column  of  blood  already  in  the 
veins.     This  pressure  is  unceasing  and  powerful. 

These  three  causes,  acting  together,  keep  up  a 
free  and  steady  flow  of  blood  in  the  veins  toward 
the  heart. 

182.  Communicating  Blood-Vessels. — In  both  ar- 
teries and  veins,  there  are  numerous  communicat- 
ing branches,  so  that,  when  a  blood-vessel  is  ob- 
structed, the  blood  passes  out  into  other  vessels  and 
around  the  point  of  stoppage,  and,  excepting  in  ex- 
traordinary cases,  the  nutrition  of  the  part  is  not  in- 
terfered with. 

183.  Recapitulation  :  Rapidity  of  the  Blood-Cur- 
rent in  the  Vessels. — The  arteries,  then,  carry  the 
bright  scarlet,  highly  oxygenated  blood  from  the 
heart  out  to  all  parts  of  the  body  for  its  nutrition. 


142  ORGANS  OF  REPAIR. 

It  is  sent  to  the  remotest  capillaries,  partly  by  the 
contraction  of  the  heart,  and  partly  by  the  elasticity 
of  the  arteries ;  from  the  arteries  it  enters  the  capil- 
laries, where  the  essential  but  very  obscure  processes 
of  nutrition  are  carried  on.     It  has  been  found  that 
the  current  of  blood  rushes  through  the  arteries 
with  an  average  velocity  of  twelve  inches  per  sec- 
ond, but,  in  consequence  of  the  smallness  of  the  cap- 
illaries and  their  distance  from  the  heart,  as  wrell 
as  the  magnitude  of  their  combined  areas  as  com- 
pared  with   that   of    the   aorta,    the   blood    moves 
through  them  very  slowly,  not  faster,  it  is  thought, 
than  one  thirtieth  of  an  inch  per  second.    When  the 
capillary  circulation  is  looked  at  through  a  micro- 
scope, as  it  may  be  in  the  wreb  of  a  frog's  foot,*  it 
is  seen  that  the  red  corpuscles  pass  along  through 
the   minute  vessels,   sometimes   two  together,   but 
oftener  in  single  file,  and  without   much  trouble  ; 
but  the  white  corpuscles  are  more  affected  by  fric- 
tion, and  drag  along,  sticking  fast  here  and  there 
until  they  are  started  again  by  the  current.     This 
slowness  of  the  current  of  blood  in  the  capillaries 
gives  time  for  the  cells  of  the  tissues  to  take  up 
what  they  want  from  the  vital  fluid,  and  deposit 
their  waste  to  be  removed,  and  so  we  find  that,  when 
the  blood  emerges  from  the  capillaries  into  the  veins, 
it  has  become  of  a  dark-purple  color,  and  unfit  for 
further  use  in  the   body  until   refreshed.     So  the 
process  wrhich  takes   place   in  the  capillaries  is  in 
some  degree  the  reverse  of  that  which  takes  place 

*  The  foot  of  a  live  frog  may  easily  be  fastened  by  strings  and  pins 
so  that  it  can  be  placed  under  the  microscope.  The  thin  membrane  is 
transparent,  and  the  circulation  of  the  blood,  as  seen  in  this  way,  is  per- 
haps the  most  surprising  and  instructive  sight  that  can  be  witnessed. 


THE  BLOOD-VESSELS.  143 

in  the  lungs.  The  blood  enters  the  lungs  of  a  black 
or  deep-purple  color  and  comes  out  bright  red.  It 
enters  the  capillaries  bright  red  and  comes  out  dark 
purple.  It  then  passes  back  to  the  heart  through 
the  veins,  the  steady  flow  being  maintained  partly 
by  the  suction  caused  in  the  act  of  respiration,  part- 
ly by  muscular  contraction  and  consequent  pressure 
on  the  veins,  and  mainly  by  the  pressure  from  the 
capillaries,  which  constantly  forces  the  blood  on- 
ward. 

184.  Peculiarity  of  Pulmonary  Artery  and  Veins. 
— There  is  one  exception  to  the  rule  that  the  arteries 
carry  scarlet  blood,  and  one  to  the  rule  that  the 
veins  carry  purple  blood.  The  pulmonary  artery 
carries  venous  blood  from  the  right  side  of  the  heart 
to  the  lungs,  and  the  pulmonary  veins  bring  back 
scarlet  or  arterial  blood  from  the  lungs  to  the  left  side 
of  the  heart. 

185,  Rapidity  of  Venous  Circulation. — The  ra- 
pidity of  the  current  in  the  veins  is  estimated  at 
about  two  thirds  of  that  in  the  arteries,  or  about 
eight  inches  per  second.  As  all  the  blood  which 
goes  out  through  the  arteries  must  return  through 
the  veins,  it  might  be  inferred  that  the  velocity  of  the 
flow  in  both  systems  of  vessels  would  be  the  same. 
If  the  capacity  of  the  vessels  were  the  same,  it  would 
necessarily  be  so,  but  there  are  generally,  with  rare 
and  unimportant  exceptions,  two  veins  returning 
the  blood  sent  out  by  one  artery,  so  that  the  capac- 
ity of  the  venous  system  is  as  a  whole  about  twice 
that  of  the  arterial,  and  the  velocity  would  be  half 
as  great ;  but,  if  we  take  into  account  the  difference 
in  the  distension  and  fullness  of  the  two  systems, 
the  estimate  given  above  is  probably  nearly  correct. 


I44  ORGANS  OF  REPAIR. 

186.  Rapidity  of  the   General   Circulation. — An 

interesting  question  arises  with  regard  to  the  ra- 
pidity of  the  general  circulation.  Experiments  have 
been  made  which  show  that  this  is  somewhat  great- 
er than  would  have  been  expected.  A  substance, 
which  remains  unaltered  in  the  blood,  and  which 
can  easily  be  detected  by  chemical  means,  was  in- 
troduced into  a  large  vein  on  the  right  side  of  a 
horse's  neck.  It  was  plainly  detected  in  the  blood 
drawn  from  the  vein  of  the  left  side,  in  from  twenty 
to  twenty-five  seconds.  In  this  short  time,  the  blood 
in  which  the  substance  was  introduced  must  have 
gone  down  to  the  right  side  of  the  heart,  from  there 
to  the  lungs,  thence  to  the  left  side  of  the  heart,  and 
thence  through  arteries  to  the  head,  before  it  en- 
tered the  vein  in  which  it  was  detected  on  its  way 
back  to  the  heart. 

The  time  required  for  all  of  the  blood  in  the 
body  to  pass  through  the  heart  can  not  be  accurate- 
ly determined,  but  only  estimated.  It  probably 
varies  very  much  with  the  vigor  of  the  heart's  ac- 
tion, the  amount  of  exercise  taken,  the  frequency  of 
the  respiration,  etc.  In  the  dead  body,  however, 
each  ventricle  is  found  to  contain  about  two  ounces 
of  fluid.  Now,  one  ventricle  is  to  be  estimated  in 
the  calculation,  because,  in  order  to  complete  the 
entire  round  of  the  body,  all  the  blood  must  pass 
through  the  left  ventricle.  If  two  ounces  enter  and 
leave  the  ventricle  at  every  contraction  of  the  heart, 
and  there  are  seventy  pulsations  in  a  minute,  one 
hundred  and  forty  ounces,  or  eight  and  three  quar- 
ter pounds,  will  pass  through  the  organ  in  this  short 
time.  Estimating,  then,  thirteen  pounds  of  blood  as 
the  average  amount  in  an  adult,  two  minutes  at  the 


THE  BLOOD-VESSELS. 


145 


most  would  suffice  for  the  completion  of  the  circu- 
lation, and  this  is  probably  pretty  near  the  truth. 

187.  The  Supply  of  Blood  in  any  Part  varies. — 
The  amount  of  blood  in  any  portion  of  the  body  at 
any  particular  time  depends  upon  certain  relations 
which  exist  between  the  blood-vessels  and  the  nerv- 
ous system.  The  walls  of  the  arteries  are  plen- 
tifully supplied  with  involuntary  muscular  fibers. 
The  contraction  of  these  fibers  diminishes  the  cali- 
ber of  the  artery.  They  are  most  abundant  in  the 
small  arteries,  and  their  contraction  or  relaxation  is 
controlled  by  certain  nerves  called  vaso-motor  nerves, 
because  they  control  or  cause  motion  in  the  ves- 
sels to  which  they  are  distributed.  If  the  nervous 
stimulus  be  such  as  to  cause  a  contraction  of  the 
arteries  supplying  any  particular  part  of  the  body, 
the  supply  of  blood  to  that  part  will  be  diminished, 
and  will  be  diminished  in  exact  proportion  to  the 
amount  of  contraction  in  the  blood-vessels.  If,  on 
the  other  hand,  the  nervous  control  be  altogether 
withdrawn,  and  the  arterial  walls  completely  re- 
laxed, the  amount  of  blood  in  the  part  affected  will 
be  increased  to  a  corresponding  extent. 

188.  The  Aorta. — The  blood  destined  for  the 
general  circulation  all  leaves  the  heart  through  the 
aorta.  This  is  a  large  vessel,  about  five  eighths  of 
an  inch  in  diameter,  with  thick,  strong  walls,  as  it 
has  to  bear  an  enormous  pressure.  It  begins  at  the 
upper  end  of  the  left  ventricle  and  on  its  right  side, 
and,  after  leaving  the  heart,  springs  upward  toward 
the  right,  near  the  breastbone,  to  the  second  rib  ; 
then  arches  backward,  and  passes  between  the  lungs 
to  the  back ;  here  it  curves  again,  and  runs  down 
along  the  spine,   through    the    diaphragm,   to   the 


146 


ORGANS  OF  REPAIR. 


/ 


1 


1 


lower  portion  of  the  abdomen — all  the  way  lying 
in  front  of  the  vertebras.  When  it  reaches  the  pel- 
vis it  divides  into  two  branches,  one  of  which  goes 
to  each  lower  extremity. 

189.  The  Femoral  Arteries. —  These  branches 
run  the  same  course  in  either  limb.  They  emerge 
from  the  abdomen  on  the  front  of  the  limb,  in  the 
groin,  not  far  beneath  the  skin,  and  pass  in  as 
straight  a  line  as  possible  on  the  inside  of  the  thigh 
to  a  point  behind  the  knee-joint,  at  about  the  middle 

of  the  hollow  space  which  is 
I  found  there  between  the  ten- 

dons on  each  side.  In  its 
course  along  the  thigh  the 
vessel  is  called  the  femoral 
artery  (Fig.  46).  At  the  knee 
it  again  divides  into  two 
branches,  one  of  which  runs 
down  in  front  of  the  leg,  and 
the  other  behind  to  the  foot, 
where  they  further  subdivide, 
to  supply  each  of  the  toes 
with  a  small  artery  on  each 
side.  All  through  this  course, 
however,  arteries  of  different 
sizes  are  given  off  as  branches 
to  supply  the  different  organs 
in  the  chest  and  abdomen,  as 
well  as  the  muscles  and  skin, 
the  course  of  the  main  arter- 
ies only  being  here  indicated. 
190.  The  Brachial  Arter- 
ies.— From  the  arch  of  the 
aorta  spring  upward  the  vessels  which  supply  the 


\\ 

\\ 

u 

It 

h 


f 


Fig.  46. — The  right  thigh. 
The  dotted  line  represents 
the  course  of  the  main  ar- 
tery 1  the  femoral). 


THE  BLOOD-VESSELS. 


147 


neck  and  head  and  upper  extremities.  Two  large 
vessels  go  to  the  arms,  one  to  each.  They  pass 
upward  and  outward  between  the  collar-bone  and 
the  first  rib,  and  dip  down 
from  the  neck,  passing  to 
the  arm  through  the  arm- 
pit. As  soon  as  the  artery 
enters  the  arm  it  is  called 
the  brachial,  and  it  con- 
tinues its  course  down  the 
inside  of  the  limb  to  the 
elbow,  where  it  comes  in 
front  (Fig.  47).  Here  it 
divides  in  two,  the  radial 
and  ulnar,  which  pass 
down,  one  on  each  side  of 
the  arm,  to  the  hand,  where 
their  subdivision  furnishes 
a  small  artery  for  each  side 
of  each  finger  and  the 
thumb.  These  vessels  also, 
throughout  their  course, 
give  off  branches  to  the 
muscles  and  other  parts. 
The  radial  artery  is  the  one  ordinarily  felt  in  order 
to  judge  of  the  pulse,  and  is  easily  found  on  the 
radial  or  thumb  side  of  the  arm,  about  an  inch  above 
the  fold  where  the  hand  bends  upon  the  arm. 

191.  The  Carotid  and  Vertebral  Arteries. — Four 
arteries  supply  the  head  and  face.  These  are  the 
two  carotid  arteries  in  front  and  the  two  vertebral 
behind.  The  two  carotids  pass  up  on  each  side  of 
the  neck,  and,  when  they  approach  the  skull,  divide 
into  two  main  branches,  one  of  which  supplies  the 


Fig.  47. — The  left  upper  arm.  The 
dotted  line  represents  the  course 
of  the  main  artery  (the  brachial). 


148  ORGANS  OF  REPAIR. 

face,  while  the  other  enters  the  skull  and  supplies 
the  brain.  The  vertebrate  supply  the  brain,  and  pass 
up  to  it  almost  the  entire  distance  inside  the  bones 
of  the  spinal  column.  It  is  important  to  know  the 
course  of  the  carotid.  There  is  a  powerful  muscle 
in  the  neck,  which  passes  upward  from  the  upper 
end  of  the  breastbone  and  parts  in  its  vicinity  to  a 
point  just  behind  the  ear,  where  it  is  attached  to  the 
skull.  Its  contraction  turns  the  head,  or,  with  other 
muscles,  bends  it  over  to  one  side  or  the  other.  Its 
outline  is  distinctly  perceptible  under  the  skin,  par- 
ticularly when  it  is  somewhat  contracted,  and  the 
head  thereby  a  little  twisted.  The  carotid  artery 
runs  very  nearly  along  the  anterior  border  of  this 
muscle,  and  its  beating  may  be  readily  felt  in  this 
situation. 

192.  The  Large  Veins. — Each  artery  is  usually 
accompanied  by  one  or  two  veins — the  largest  by 
one,  and  the  smaller  ones  by  two.  The  veins  are 
called,  as  a  rule,  by  the  same  name  as  the  correspond- 
ing artery,  the  most  notable  exception  to  this  being 
the  jugular  veins,  which  are  the  companions  of  the 
carotid  arteries,  and  run  close  by  their  side.  All  the 
blood  from  the  lower  part  of  the  body  is  finally  col- 
lected in  a  large  vein,  called  the  vena  cava  inferior, 
which  runs  up  the  spine  beside  the  aorta,  while  that 
from  the  head,  neck,  and  upper  extremities  is  col- 
lected in  the  vena  cava  superior,  and  both  these  large 
veins  discharge  their  contents  into  the  right  auricle 
of  the  heart.  The  veins  which  take  the  blood  from 
the  digestive  organs  unite  to  form  the  portal  vein, 
which  enters  the  liver,  and  the  large  vein  which 
emerges  from  the  liver  joins  the  vena  cava  inferior,  so 
that  all  the  blood  from  the  digestive  organs  must  go 


THE  BLOOD-VESSELS.  lA^ 

through  the  liver  before  it  enters  the  general  circu- 
lation. 

The  pulmonary  artery,  soon  after  it  leaves  the 
right  ventricle,  divides  into  two  branches,  one  of 
which  passes  under  the  arch  of  the  aorta,  before  de- 
scribed, to  the  right  lung,  and  the  other  goes  to  the 
left  lung.  The  corresponding  pulmonary  veins  are 
two  from  each  lung,  and  they  empty  their  contents 
into  the  left  auricle. 


CHAPTER   X. 

DISORDERS   OF  CIRCULATION. — HEMORRHAGE. 

193.  Obstruction  of  the  Circulation. — If  a  cord 
be  tightly  bound  about  a  finger,  that  part  of  the 
member  which  is  farthest  from  the  heart  will  soon 
become  livid  and  begin  to  swell.  This  effect  is  due 
to  the  difference  in  structure  and  position  of  the  ar- 
teries and  veins.  The  arteries  are  tubes  with  stiff, 
elastic  walls,  and  do  not  usually  lie  very  near  the 
surface,  whereas  the  veins  have  thin,  inelastic  walls, 
and  many  of  them  are  very  superficial.  The  conse- 
quence is  that  it  is  a  somewhat  difficult  matter  to 
compress  an  artery  so  as  to  entirely  prevent  the 
flow  of  blood  through  it,  while  the  veins  are  very 
easily  compressed.  In  binding  a  cord  around  the 
finger,  then,  unless  great  force  be  applied,  the  veins 
are  compressed  and  the  current  of  blood  in  them 
checked,  while  that  in  the  arteries  is  not  at  all  or 
only  slightly  interfered  with,  so  that  blood  is  being 
continually  carried  into  the  finger,  and  can  not  flow 
out.  The  accumulation  of  blood  in  the  part  ac- 
counts for  the  swelling,  and  the  dark  color  is  that  of 
venous  blood.  If,  now,  the  cord  be  removed,  the 
swelling  does  not  immediately  disappear,  because 
wherever  there  is  a  damming  of  the  current  of  blood 
so  that  its  flow  in  the  veins  is  interfered  with,  after 


DISORDERS  OF  CIRCULATION.  151 

the  vessels  become  distended  to  a  certain  point,  the 
pressure  on  their  walls  is  relieved  by  the  loss  of  a 
portion  of  their  contents.  The  serum  of  the  blood 
begins  to  pass  through  the  walls  of  the  veins  into 
the  tissues  outside  of  them,  producing  the  condition 
called  dropsy*  When  the  circulation  of  the  part  is 
restored,  all  this  serum  which  has  left  the  vessels 
has  to  be  reabsorbed,  partly  by  the  blood-vessels 
and  partly  by  the  lymphatics,  and  this  occupies  an 
appreciable  time. 

Now,  let  us  suppose  that  this  obstruction,  instead 
of  being  applied  to  the  veins  on  the  surface  of  the 
body,  is  situated  in  some  of  the  interior  organs.  It 
is  plain  that  a  similar  effect  will  be  produced  if  the 
supply  of  blood  to  any  part  remains  the  same,  while 
the  return  of  it  is  prevented.  Such  obstructions  are 
most  common  in  the  heart  and  lungs,  as  a  result  of 
disease  in  those  parts. 

194.  Disease  of  the  Heart. — Let  us  suppose  that 
the  valves  between  the  left  auricle  and  left  ventricle 
have  been  inflamed,  and  have  become  so  altered  in 
their  shape  and  size  that,  when  the  heart  contracts 
to  force  the  blood  from  the  left  ventricle  into  the 
aorta,  they  do  not  completely  close  the  opening.  It 
is  plain  that  a  portion  of  the  blood  will  be  forced 
backward  into  the  auricle.  This  regurgitation,  as 
physicians  call  it,  takes  place  at  every  beat  of  the 
heart,  and  as  the  auricle  is  in  this  way  kept  filled 
with  blood,  and  a  sort  of  conflict  continually  takes 
place  between  the  current  coming  into  it  from  the 

*  When  fluid  passes  in  this  way  from  the  interior  of  the  blood- 
vessels through  their  walls  into  the  tissues  outside  of  them,  the  fibrin 
does  not  form  a  part  of  it.  In  other  words,  it  is  not  the  plasma  that  is 
effused,  but  the  scrum. 


152  ORGANS  OF  REPAIR. 

lungs  and  that  coming  back  to  it  from  the  ventricle, 
the  current  in  the  pulmonary  veins  is  materially 
interfered  with.  In  short,  the  blood  is  dammed 
backward  into  the  lungs.  Here,  then,  is  an  actual 
obstruction  to  the  circulation,  as  much  as  there  is 
when  we  tie  a  string  around  the  finger.  The  result 
can  be  easily  ascertained  by  following  backward 
the  course  of  the  circulation.  The  obstruction  to 
the  exit  of  blood  from  the  lungs  causes  the  blood 
to  accumulate  in  that  organ — in  other  words,  pro- 
duces a  congestion  there.  The  blood,  not  being 
changed  frequently  enough,  does  not  get  enough 
oxygen,  and  the  person  is  obliged  to  breathe  faster 
in  order  to  supply  more.  This  we  call  shortness  of 
breath.  The  accumulation  of  blood  in  the  lungs, 
in  a  measure,  obstructs  the  current  of  blood  which 
comes  to  them  through  the  pulmonary  artery.  The 
blood  in  the  pulmonary  artery  being  hindered  in  its 
course,  the  right  ventricle  is  not  able  to  empty  it- 
self perfectly,  becomes  dilated,  and  its  walls  become 
thinned.  The  obstruction  at  this  point  prevents  the 
right  auricle  from  emptying  itself  properly,  and 
this  interferes  with  the  free  return-current  in  the 
large  veins  which  are  connected  with  it.  Thus  the 
flow  of  blood  is  hindered  in  the  veins  from  all  parts 
of  the  body  by  the  disease  of  one  set  of  valves.  The 
obstruction  of  the  venous  flow  brings  about  the 
same  results  that  we  have  observed  in  the  con- 
stricted finger.  The  face  becomes  more  or  less 
livid,  the  lips  and  finger-nails  bluish,  and  the  serum 
of  the  blood  passes  out  into  the  tissues  around  the 
veins,  causing  general  dropsy.  This  is  the  most  com- 
mon form  of  heart-disease,  and  it  has  been  somewhat 
minutely  described,  in  order  to  show  how  purely 


DISORDERS  OF  CIRCULATION.  153 

mechanical  are  some  of  the  diseases  to  which  we 
are  subject.  There  are  other  forms  of  disease  of 
the  valves,  whose  effects  may  be  traced  by  those 
curious  in  such  things.  The  aortic  valves,  for  ex- 
ample, may  be  affected  so  as  to  close  incompletely, 
and  allow  a  part  of  the  contents  of  the  aorta  to  be 
forced  back  into  the  ventricle  by  the  elasticity  of 
the  artery  every  time  the  heart  relaxes.  On  the 
other  hand,  these  same  valves  may  be  made  so  rigid 
by  disease  that,  although  they  close  tightly  enough 
to  keep  the  current  of  blood  from  setting  back 
through  them,  they  do  not  open  sufficiently  wide 
to  allow  a  free  flow  through  them  during  the  heart's 
contraction.  This  latter  form  of  disease  is  one  of 
the  most  common,  and  gives  rise  to  symptoms  very 
much  like  those  of  the  disease  which  has  been  more 
fully  described  above.  Sometimes,  as  a  result  of 
inflammation  of  a  peculiar  kind,  the  edges  of  the 
valves  have  small,  wart-like  masses  attached  to  them. 
These  little  masses  sometimes  prevent  the  valves 
from  closing  properly,  and  sometimes  not,  but  they 
always  offer  more  or  less  obstruction  to  the  circu- 
lation. Occasionally  one  of  these  bodies  becomes 
detached  from  the  valve  by  the  force  of  the  blood- 
current,  and  is  whirled  away  through  the  body. 
As  the  current  of  blood  in  the  arteries  is  continually 
in  the  same  direction,  and  they  grow  smaller  and 
smaller,  such  a  little  body  at  length  reaches  a  spot 
where  the  caliber  of  the  artery  is  too  small  to  let  it 
through.  It  plugs  up  the  artery.  This  gives  rise  to 
different  consequences,  according  to  circumstances. 
Sometimes  the  circulation  is  carried  on,  in  spite  of 
the  obstruction,  by  other  arteries  which  pass  around 
the  point  of  plugging  ;  and  sometimes  the  part  which 


154  ORGANS  OF  REPAIR. 

receives  its  supply  of  blood  from  the  affected  ar- 
tery, being  thus  suddenly  deprived  of  it,  dies,  fall- 
ing into  the  condition  known  as  gangrene. 

195.  How  Heart-Disease  is  detected.  —  All  of 
these  affections  of  the  valves  of  the  heart,  interfering 
as  they  do  with  the  free  flow  of  the  blood,  give  rise 
to  sounds  of  greater  or  less  intensity,  the  varieties 
of  which  are  familiar  to  practicing  physicians,  and 
indicate  to  them  quite  accurately  the  character  and 
extent  of  the  disease. 

106.  Effect  of  the  Coagulation  of  the  Blood. — 
Whenever  the  surface  of  the  body  is  wounded, 
blood-vessels  are  necessarily  severed,  and,  if  there 
were  no  means  of  stopping  the  consequent  escape 
of  blood,  it  would  not  take  very  long  for  the  whole 
body  to  be  drained.  The  fibrin  of  the  blood,  how- 
ever, by  its  property  of  coagulation,  serves  to  arrest 
bleeding.  All  of  the  methods  used  by  surgeons  to 
stop  haemorrhage  in  any  part  of  the  body  have  for 
their  object  the  coagulation  of  the  blood. 

197.  Conditions  of  Coagulation. — Blood  coagu- 
lates much  more  rapidly  on  a  rough,  ragged  sur- 
face than  on  a  smooth  one,  and  in  a  wound  that  is 
much  bruised  or  lacerated  there  is  often  very  little 
bleeding,  even  from  large  arteries.  Instances  have 
been  known  in  which  the  arm  has  been  violently 
torn  from  the  body  by  machinery,  and  the  brachial 
artery  divided,  with  comparatively  little  bleeding ; 
although,  if  the  arm  were  cut  off,  without  controlling 
the  main  artery,  the  person  would  die  of  haemor- 
rhage in  a  few  minutes.  In  a  clean-cut  wound  the 
haemorrhage  is  often  very  severe  from  small  blood- 
vessels, and  almost  always  needs  some  artificial 
control. 


HEMORRHAGE. 


155 


198.  Arterial  and  Venous  Haemorrhage. — When 
an  artery  has  been  severed,  it  is  not  difficult  for  one 
who  understands  the  circulation  to  detect  it.  In 
the  first  place,  the  arterial  blood  is  of  a  bright  scar- 
let color,  and,  in  the  second  place,  it  comes  from  the 
vessel  in  jets  or  spurts.  The  blood  in  the  veins  is 
dark  purple,  and,  as  the  veins  do  not  pulsate  like 
the  arteries,  it  flows  from  the  wound  in  a  steady, 
uniform  stream.  The  force  with  which  the  blood 
issues  from  a  cut  artery  is  surprising.  A  jet  from 
one  of  the  little  arteries  of  a  finger  will  spurt  at 
least  a  foot  in  a  stream  no  bigger  than  a  knitting- 
needle.  A  vein  never  bleeds  in  spurts.  In  a  wound, 
however,  both  veins  and  arteries  may  be  severed 
and  the  blood  mixed,  although  usually  either  the 
arterial  or  venous  color  predominates.  If  the  blood 
from  the  wound  be  soaked  up  by  a  sponge  or  soft 
cloth,  an  arterial  spurt  can  be  seen  before  the  cut 
fills  up  again  with  blood. 

199.  Natural  Arrest  of  Haemorrhage. — If  a  wound 
be  left  to  itself,  the  following  are  the  means  pro- 
vided by  Nature  to  arrest  bleeding :  When  an 
artery  is  cut,  its  walls  always  contract  somewhat, 
so  that  its  caliber  is  diminished.  The  elasticity 
of  the  artery  also  draws  it  backward  to  some  ex- 
tent into  the  flesh.  In  the  smallest  arteries,  these 
acts  are  often  sufficient  to  stop  the  bleeding  en- 
tirely. In  every  case  they  resist  the  current,  make 
it  move  more  slowly,  and  so  favor  coagulation. 
When  a  vein  is  cut,  the  walls,  being  thin  and  in- 
elastic, collapse,  the  opposite  sides  coming  in  con- 
tact and  tending  to  obstruct  the  flow  of  blood.  In 
these  ways  the  current  of  blood  from  all  cut  vessels 
is  diminished  in  force.    The  blood  begins  to  coagu- 


156  ORGANS  OF  REPAIR. 

late  almost  immediately,  and  this  offers  still  further 
resistance  to  the  out-coming  current.  If  the  bleed- 
ing continues,  and  the  blood-vessels  are  so  drained 
that  the  brain  feels  the  lack  of  blood,  the  person 
faints,  the  nervous  force  of  the  heart  is  diminished, 
and  in  this  way  also  the  force  of  the  flow  is  less- 
ened. This  is  Nature's  last  resort,  and,  if  the  ves- 
sels injured  are  so  large  that  these  means  are  not 
sufficient  to  stop  the  flow,  the  person  will  bleed  to 
death. 

200.  Artificial  Arrest  of  Haemorrhage  ;  Cold. — 
The  artificial  means  which  we  have  at  our  com- 
mand for  arresting  haemorrhage  merely  aim  to  as- 
sist these  attempts  of  Nature. 

The  application  of  cold  to  any  part  of  the  body 
produces  pallor,  caused  by  a  diminution  in  the  sup- 
ply of  blood  to  the  part.  This  is  owing  to  the  fact 
that  the  stimulus  of  cold  causes  contraction  of  the 
smaller  blood-vessels,  and  so  lessens  the  amount  of 
blood  in  them.*  When  a  cut  surface  is  exposed  to 
the  air,  if  the  vessels  which  have  been  severed  are 
small,  the  coldness  of  the  air  is  sometimes  sufficient 
to  stop  the  bleeding  by  causing  a  contraction  of  the 
vessels.  This  effect  can  be  increased  by  bathing 
the  wound  in  cold  water.  If  this  be  done,  however, 
the  cut  surface  should  not  be  wiped  or  rubbed  with 
the  sponge  or  towel,  for  fear  that  the  already  co- 
agulated blood,  which  begins  to  form  an  obstruc- 
tion to  the  flow,  may  be  washed  away. 

201.  Styptics.  — We  also  have  artificial  means  of 
bringing  on  coagulation  of  the  blood.     The  sub- 

*  The  diminution  in  the  caliber  of  arteries  in  such  cases  is  caused 
by  the  contraction  of  the  involuntary  muscular  fibers  which  surround 
them,  as  previously  explained. 


H^EMORRHA  GE.  157 

stances  used  for  this  purpose  are  called  styptics. 
The  persulphate  of  iron  is  an  exceedingly  power- 
ful one.  The  muriatcd  tincture  of  iron  is  another. 
A  turn,  or  tannic  acid,  or  any  other  astringent,  pro- 
duces the  same  effect.  The  great  objection  to  all 
of  these  substances  is,  that  they  so  alter  the  tissues 
with  which  they  come  in  contact  that  the  wound  is 
often  hindered  from  healing  as  rapidly  as  it  other- 
wise would.  They  are  mostly  used  when  it  is  im- 
possible to  apply  actual  pressure  upon  the  bleeding 
vessels. 

202.  Compression. — Compression  is  the  most  per- 
fect and  unobjectionable  method  of  arresting  haemor- 
rhage. This  brings  no  outside  injurious  matter  in 
contact  with  the  wounded  surface,  and  acts  merely 
by  stopping  the  flow  temporarily  until  Nature  has 
time  to  stop  it  permanently. 

If  the  wound  be  small,  and  can  be  covered  by 
the  finger,  it  will  generally  be  enough  to  put  the 
finger  or  thumb  immediately  on  the  cut  and  press 
toward  a  bone  until  the  bleeding  stops.  If  the 
wound  be  too  large  for  this,  pressure  must  be  made 
at  a  point  outside  of  the  wound,  where  the  vessels 
which  are  supposed  to  be  cut  are  known  to  run." 
If  the  bleeding  be  venous,  of  course  the  current  is 
running  toward  the  heart,  and  the  pressure  must 
be  made  on  the  side  farthest  from  that  organ.  If 
the  haemorrhage  be  arterial,  the  pressure  must  be 
made  between  the  wound  and  the  heart.     In  the 

*  Or  some  soft,  porous  material,  such  as  a  towel,  handkerchief, 
sponges,  or  cotton  cloth  or  batting,  may  be  crowded  into  the  wound 
and  held  there  by  the  hand  or  a  bandage.  This  is  often  the  easiest 
way  to  apply  pressure  directly  to  the  mouths  of  the  bleeding  vessels. 
Woolen  material  is  too  rough  and  stiff  for  this  purpose. 


158  ORGANS  OF  REPAIR. 

case  of  venous  haemorrhage,  a  comparatively  slight 
pressure  will  generally  be  sufficient,  as  the  walls  of 
the  veins  possess  little  resisting  power,  and  are 
readily  forced  into  contact.  On  the  arteries,  how- 
ever, greater  force  is  necessary,  and  it  is  sometimes 
surprisingly  difficult  to  fix  the  vessel  and  compress 
it.  It  is  to  be  remembered  that  in  the  limbs  the 
course  of  the  arteries  is,  in  the  main,  nearly  straight 
and  lengthwise  of  the  limb,  so  that  all  that  it  is  ne- 
cessary to  do  in  case  of  severe  arterial  haemorrhage 
is  to  feel  along  the  outer  edge  of  the  wound,  an 
inch  or  so  from  it,  pressing  the  finger  down  deeply 
until  the  artery  is  felt  pulsating,  and  then  compress 
it  against  the  nearest  bone. 

203.  Permanent  Arrest  of  Haemorrhage. — When 
the  haemorrhage  has  thus  been  temporarily  arrested, 
the  pressure  must  in  some  way  be  kept  up  until 
there  is  no  danger  of  a  fresh  burst  on  its  removal. 
Nature's  method  of  permanently  arresting  bleeding 
is  this :  It  has  been  before  stated  that  blood  will 
coagulate  not  only  outside  the  vessels,  but  inside 
them,  if  its  free  motion  is  interfered  with.  Now,  if 
from  the  contraction  of  the  vessels,  or  coagulation 
of  the  blood  which  has  flowed  from  them,  or  in  con- 
sequence of  pressure  artificially  applied,  or  for  any 
other  reason,  the  current  of  blood  in  the  artery  is 
stopped  at  the  severed  end,  the  fibrin  of  the  blood 
begins  very  soon  to  coagulate  inside  the  vessel,  and 
this  coagulation  extends  from  the  cut  end  backward 
toward  the  heart  to  a  point  where  the  circulation 
becomes  free  and  unobstructed,  that  is,  to  the  point 
at  which  some  branch  artery  is  given  off  from  the 
wounded  one  (Fig.  48).  Thus  the  coagulum  (or 
clot)  formed  will  vary,  according  to  circumstances, 


HEMORRHAGE.  1 59 

from  an  eighth  of  an  inch  or  less  to  an  inch  in 
length.  If  the  compression  or  other  obstruction 
continues  long  enough  to  allow  of  it, 
this  coagulum  becomes  firmly  at- 
tached to  the  inside  of  the  vessel,  and 
forms  a  plug  which  effectually  and 
permanently  closes  it,  and,  as  the 
wound  heals,  this  plug  and  the  walls 
of  the  now  useless  artery  become  grad- 
ually absorbed  until  a  mere  thread 
remains,  and  even  this  may  disappear 
so  as  to  leave  no  trace  of  the  vessel 
which  formerly  existed.  But  it  is  to 
be  considered  that  during  the  forma-  FlG-  48.— ciot  in 
tion  of  this  plug,  and  its  attachment  to  j^  X^lxxsA 
the  walls  of  the  vessel,  it  has  to  re- 
ceive the  impulse  of  the  blood  continually  driven 
against  it  seventy  times  a  minute  by  the  heart ; 
and  in  large  vessels  this  blow  is  a  very  strong 
one ;  so  that,  if  the  pressure  be  removed  from 
an  artery  too  soon,  even  after  this  coagulum  is 
formed,  the  impulse  of  the  current  of  blood  may 
be  sufficient  to  drive  out  the  plug,  and  bleeding 
will  begin  again.  This  danger  is  absent  in  venous 
haemorrhage,  and  it  is  a  general  rule  that  if  such 
haemorrhage  is  once  stopped  it  will  not  recur.  But 
in  arteries  this  is  a  peril  that  must  always  be 
guarded  against,  and  surgeons  accomplish  what 
they  want  by  tying  the  end  of  the  bleeding  artery 
with  a  string.  Ligatures,  made  expressly  for  this 
purpose,  are  used,  and  although  they  are  finally 
discharged  from  the  wound  with  the  secretions, 
showing  that  they  have  cut  through  the  walls  of 
the  vessel  around  which  they  were  tied,  they  re- 


160  ORGANS  OF  REPAIR. 

main  long  enough  to  accomplish  the  purpose*  A 
person's  finger  soon  becomes  exhausted  by  con- 
tinual exertion  in  maintaining  pressure,  but  a  liga- 
ture keeps  the  artery  closed  for  several  days  before 
it  comes  away,  and  thus  ample  time  is  afforded  for 
the  permanent  closing  of  the  vessel  in  the  way 
above  described.  The  application  of  a  ligature  re- 
quires special  knowledge  and  skill,  and  should  only 
be  attempted  by  a  surgeon. 

204.  Recapitulation. — The  means  at  everybody's 
hand,  then,  for  arresting  haemorrhage  are  these : 

1.  The  application  of  cold  by  water,  ice,  or  air. 

2.  Pressure  by  the  finger,  thumb,  bandage,  or  in 
any  way  that  suggests  itself. 

(a.)  If  the  wound  be  small,  pressure  on  the  wound 
itself. 

(b.)  If  the  wound  be  large,  and  the  bleeding 
from  the  veins,  pressure  on  the  side  farthest  from 
the  heart,  or  by  plugging  the  wound  full  of  some 
soft  material.  If  the  blood  comes  from  an  artery, 
pressure  on  the  side  nearest  the  heart. 

(c.)  Pressure  to  be  kept  up  until  the  bleeding 
stops,  or  until  some  means  can  be  applied  to  make 
the  pressure  permanent. 

3.  Styptics  or  astringents.  These  are  to  be  used 
chiefly  where  pressure  can  not  be  applied,  and  after 
the  application  of  cold  has  proved  insufficient. 

205.  Wounds  of  the  Extremities. — Wounds  of 
the  extremities  often  bleed  profusely.  Usually,  di- 
rect pressure  on  the  spot  of  the  wound  will  suffice 

*  Surgeons  are  now  in  the  habit  of  using  ligatures  made  of  some 
animal  material,  such  as  catgut  or  chamois-leather,  which  does  not 
irritate  the  wounded  parts,  and  is  gradually  absorbed,  so  that  the  wound 
can  be  completely  closed  when  first  dressed. 


HEMORRHAGE. 


161 


to  check  it.  If,  however,  the  wounded  vessel  is  so 
large  that  it  bleeds  in  spite  of  this,  the  main  artery 
must  be  compressed  above  the  wound.  It  has  been 
already  shown  that  the  artery  is  a  single  trunk 
only  in  the  upper  part  of  each  limb — i.  e.,  from  the 
shoulder  to  the  elbow  in  the  arm,  and  from  the 
groin  to  the  space  behind  the  knee  in  the  lower  ex- 
tremity. Somewhere  in  this  course,  then,  the  ves- 
sel must  be  compressed  against  the  bone  beneath ; 
for  below  the  elbow  and  knee  the  artery  divides, 
and  the  branches  are  so  sit- 
uated that  they  can  not  be 
compressed.  The  brachial 
and  femoral  arteries — that 
is,  the  arteries  of  the  upper 
arm  and  thigh — are  so  large 
and  strong,  and  receive 
such  a  strong  impulse  from 
the  heart,  besides  being  in 
a  measure  protected  by  the 
surrounding  tissues,  that 
they  can  not  be  compressed 
by  the  fingers  to  any  advan- 
tage. The  best  method  yet 
devised  is  the  use  of  a 
knotted Jiandkcrcliief 'or  other 
bandage,  a  rope  or  cord  be- 
ing SO  Small  as  tO  CUt  the  FlG-  49-— Manner  of  compressing 
n      t  -i    .,  i  r  ' .  an  artery  with  a  handkerchief 

tiesh,  and  therefore  unsuit-        and  stick. 
able  (Fig.  49).     A  handker- 
chief should  be  tied  loosely  around  the  limb,  with 
a  hard  knot  over  the  artery.     Immediately  under- 
neath the  knot  should  be  placed  another  handker- 
chief, folded  so  as  to  form  a  pad  about  two  inches 


1 62  ORGANS  OF  REPAIR. 

wide  and  three  long,  to  keep  the  knot  from  bruising 
the  flesh  when  the  handkerchief  is  tightened  (Fig. 
50).     The  handkerchief  should  be  loosely  tied  in  the 


-AHTERY 


Fig.  50. — Direct  compression  of  a  wound  by  means  of  what  surgeons  call 
a  graduated  compress,  made  of  pads  of  cloth,  folded  in  different  sizes, 
with  the  largest  one  on  top. 


first  place,  so  as  to  allow  a  stick  or  rod  to  be  in- 
troduced between  it  and  the  skin  for  the  purpose 
of  twisting  it.  The  stick  or  lever  should  be  placed 
at  some  distance  from  the  compressing  knot,  and  it 
is  better  to  put  it  on  the  outside  of  the  limb,  where 
nothing  will  interfere  with  the  twisting.  The  stick 
is  now  to  be  twisted  round  and  round,  making  the 
handkerchief  tighter  and  tighter  and  the  knot  press 
down  deeper  and  deeper,  until  finally  the  artery  will 
be  compressed  between  the  knot  and  the  bone,  and 
the  haemorrhage  will  cease.  This  method  of  com- 
pression is  effectual  and  easy  of  application,  but  of 
course  is  only  temporary,  for  such  complete  encir- 
cling of  a  limb  and  entire  stoppage  of  the  circula- 
tion produces  gangrene  if  too  long  continued. 

206.  Fainting. — When,  for  any  reason,  the  supply 
of  blood  to  the  brain  is  insufficient  for  its  nutrition, 
the  person  faints.  In  our  ordinary  erect  position, 
the  blood  has  to  be  driven  upward  by  the  heart  for 
a  foot  or  more,  in  opposition  to  the  force  of  grav- 
ity. In  a  fainting  person  there  is  not  power  enough 
to  do  this,  and  we  must  relieve  the  heart  of  a  cer- 


HEMORRHAGE.  163 

tain  amount  of  its  burden.  We  accomplish  this  end 
by  laying  the  person  flat  on  his  back,  without  rais- 
ing the  head  by  a  pillow  or  rest  of  any  kind.  In 
this  position  the  blood  readily  reaches  the  brain, 
and  that  organ  rapidly  recovers  its  functions. 

207.  Shortness  of  Breath. — Shortness  of  breath 
always  indicates  that  the  blood  contains  too  little 
oxygen.  When  we  are  short  of  breath  from  exer- 
cise, it  is  due  to  the  fact  that  our  bodies  have  made 
more  waste  material  than  usual,  which  the  blood 
has  been  unable  to  get  rid  of,  and  also  that  the  oxy- 
gen taken  in  from  the  lungs  is  insufficient  for  the 
needs  of  the  wasting  tissues.  In  other  words,  we 
are  wearing  out.  Then  we  begin  to  breathe  faster, 
and  thus  try  to  get  rid  of  more  waste  and  take  in 
more  fresh  material.  But,  if  the  exercise  which  pro- 
duces the  excess  of  waste  be  continued,  the  time 
comes  when  we  can  not  breathe  rapidly  enough  to 
dispose  of  it,  the  body  becomes  limp,  and  we  are 
forced  to  rest  and  recover.  After  we  have  com- 
pletely ceased  our  exertions  the  rapidity  of  breath- 
ing continues  for  a  time,  making  the  supply  much 
greater  than  the  waste,  and  gradually  expelling  the 
latter  from  the  body  until  the  balance  between  the 
two  has  become  even  again  and  the  parts  are  all  in 
their  natural  condition.  In  diseases  of  the  lungs 
which  render  parts  of  these  organs  useless,  such 
as  pneumonia,  consumption,  etc.,  the  same  effect  is 
produced.  When  we  have  only  half  as  much  lung 
to  breathe  with,  we  have  to  breathe  much  faster  to 
make  up  the  deficiency. 


PART     IV. 
ORGANS  OF  CO-ORDINATION. 


CHAPTER   I. 

NERVE-SUBSTANCE. 

208.  Difficulty  of  Investigation. — The  nervous  sys- 
tem is  less  thoroughly  understood  than  almost  any 
other  portion  of  the  body.  The  difficulties  of  in- 
vestigation are  enormous,  and  its  functions  are  so 
intimately  connected  with  the  phenomena  of  con- 
scious life  that,  with  the  exception  of  a  few  facts  on 
which  all  observers  are  agreed,  the  truth  is  buried 
under  a  mass  of  conflicting  theories,  which  the 
earnest  and  tireless  efforts  of  patient  workers  all 
over  the  world  are  not  yet  able  to  remove.  We 
shall  occupy  ourselves  mainly  with  what  are  ac- 
cepted facts. 

209.  The  Two  Divisions  of  the  Nervous  Sys- 
tem.— We  have  seen,  in  previous  chapters,  that  cer- 
tain operations  constantly  go  on  in  our  bodies,  not 
only  without  our  willing  them,  but  without  our 
consciousness.  Such  are  the  processes  of  digestion, 
circulation,  etc.  Our  voluntary  acts,  those  which 
are  the  result  of  and  accompanied  by  conscious- 
ness, constitute,  in  fact,  the  smallest  part  of  what 
goes  on  within  us.     Now,  the  organs  which  are  un- 


NER  VE-S  UBS  TANCE.  165 


Fig.  B. — The  cerebrospinal  system  of  nerves. 


1 66 


ORGANS  OF  CO-ORDINATION. 


der  voluntary  control  arc  called  the  organs  of  animal 
life,  while  those  which  are  beyond  our  control  are 
known  as  those  of  organic  life.  Corresponding  to 
these  two  divisions  of  the  body  are  two  great  di- 
visions of  the  nervous  system — one  of  which  has 
charge  of  the  organs  of  animal  life,  and  is  called  the 
cerebrospinal  system,  while  the  other  regulates  the 
processes  of-  organic  life,  and  is  called  the  sympa- 
thetic system.  The  name  of  the  former  indicates  the 
fact  that  it  comprises  the  cer'ebrum,  or  brain,  and  the 
spinal  cord,  with  the  nerves  proceeding  from  them  ; 
and  the  name  of  the  latter  suggests  one  of  the  prin- 
cipal characteristics  of  that  portion  of  the  nervous 
system,  viz.,  that  of  inducing  and  regulating  a  sym- 
pathy between  different  organs,  as  wTill  be  hereafter 
explained. 

210.  Nervous  Tissue. — Nervous  tissue,  wherever 
it  is  found,  is  made  up  of  so-called  white  matter,  or 
gray  matter,  or  of  both  combined. 

211.  Nerve-Fibers. — The  white  matter  is  found, 

on  close  examination,  to 
be  made  up  of  slender 
fibers,  running  parallel  to 
each  other  (Fig.  5 1).  They 
vary,  according  to  their 
situation,  from  the  20100 
to  the  4^o0  of  an  inch 
in  diameter,  are  nearly 
cylindrical  in  shape,  and 
have  for  an  outer  layer  a 
thin,  delicate  membrane, 
which  serves  to  protect 
the  nerve-substance  and  retain  it  in  shape.  Just  in- 
side the  membranous  covering  is  an  almost  trans- 


FlG.  51. — Nerve-fibers. 


NER  VE-S  UB  STANCE. 


167 


parent  material,  which,  after  death,  appears  to  co- 
agulate and  becomes  whitish  and  slightly  granular. 
This  is  called  the  my' din,  or,  by  others,  the  white 
substance  of  Schwann^  from  the  man  who  first  de- 
scribed it.  In  the  center  of  the  whole  runs  a  slen- 
der thread  of  transparent,  very  finely  granular  mat- 
ter, called  the  axis-cylinder.  This  latter  substance, 
in  all  probability,  serves  for  the  actual  conduction 
of  the  nervous  influence,  whatever  it  may  be,  and 
the  white  substance  of  Schwann,  or  myelin,  proba- 
bly acts  as  an  insulator.  These  distinctions  be- 
tween the  different  portions  of  a  nerve-fiber  are  not 
visible  in  the  living  body,  but  are  the  result  of 
changes  which  take  place  after  the  nerve  has  been 
separated  from  its  connections,  probably  from  a 
sort  of  coagulation. 

212.  Nerve-Cells.  —  The  gray  matter  does  not 
consist  of  fibers,  but  of 
cells  (Fig.  52)  imbedded 
in  a  mass  of  granular  mat- 
ter. These  cells  vary  in 
size  from  ^  to  Y-^  of 


an  inch  in  diameter,  and 
each  contains  a  nucleus 
and  nucleolus,  usuallyvery 
distinctly  marked.  Each 
cell  also  has  prolonga- 
tions which  extend  from 
its  circumference  in  vari- 
ous directions,  and  are  supposed  in  every  instance 
to  connect  either  with  a  nerve-fiber  or  with  some 
other  cell.  These  prolongations  vary  in  number 
from  one  up  to  five  or  six,  and,  as  they  are  traced 
along  their  course  with  the  aid  of  the  microscope, 


Fig.  52. — Nerve-cells. 


1 68  ORGANS  OF  CO-ORDINATION. 

they  arc  seen  to  divide  and  subdivide  until  they 
become  too  small  to  follow.  It  is  supposed  that 
every  nerve-fiber  is  connected  with  such  a  cell. 

The  nerve-fibers,  above  described,  constituting 
the  white  nerve-matter,  are  mere  conductors  of  the 
nerve-force.  They  constitute  the  means  of  commu- 
nication between  the  outside  of  the  body  and  the 
nerve-centers.  The  nerve-centers,  on  the  other  hand, 
are  made  up  of  gray  matter,  and  are  the  originators 
of  nerve-force.  So  we  see  that  the  nervous  system, 
like  the  rest  of  the  body,  is  made  up  of  cells  and 
fibers,  and  that  the  essential  part  of  the  whole  is 
the  cell,  the  fiber  playing  a  very  subordinate  role. 

213.  Structure  of  the  Nerves. — A  nerve  which 
is  large  enough  to  be  seen  by  the  naked  eye  is  com- 
posed of  a  great  number  of  the  fibers  above  de- 
scribed, lying  side  by  side  and  bound  together  by 
a  considerable  amount  of  connective  tissue.  The 
connective  tissue  is  greatest  in  amount  in  situations 
where  the  nerve  is  most  exposed  to  injury — for  ex- 
ample, in  the  limbs.  In  the  brain,  on  the  other 
hand,  and  in  the  spinal  cord,  where  the  nerve- 
substance  is  protected  by  a  strong  bony  covering, 
the  amount  of  connective  tissue  is  scanty  and  the 
fibers  are  very  small. 

The  white  nerve-matter  constitutes  much  the 
larger  part  of  the  whole  nervous  system.  It  forms 
the  great  nerve-trunks  which  go  to  the  limbs  and 
to  the  exterior  of  the  body  in  every  direction,  and 
also  forms  the  greater  part  of  the  brain  and  spinal 
cord. 

214.  Ganglia. — The  gray  matter,  however,  forms 
an  important  part  of  the  brain  and  spinal  cord,  and 
also  of  various  small  nerve-centers,  called  ganglia, 


NER  VE-SUB  STANCE.  1 69 

which  are  scattered  throughout  the  body.  In  fact, 
every  collection  of  gray  matter,  which  is  separated 
from  other  masses  of  gray  matter  by  intervening 
white  matter,  is  called  a  ganglion,  and  so  even  the 
different  parts  of  the  brain  are  included  under  this 
name. 

215.  Function  of  Nerve-Fibers. — The  function 
of  the  nerve-fibers,  as  has  been  stated,  is  to  convey 
impressions  from  one  end  to  the  other.  Each  nerve- 
fiber,  even  in  the  largest  bundle,  is  completely  iso- 
lated from  all  others,  and  runs  an  uninterrupted 
course  from  the  cell,  where  it  takes  its  origin,  to 
the  point  of  its  termination.  At  its  termination,  it 
receives  an  impression,  and  this  impression  acts  as 
a  stimulus,  which  produces  some  molecular  change 
through  the  whole  length  of  the  nerve,  and  event- 
ually in  the  cell  from  which  it  comes.  How  this 
communication  is  accomplished  is  not  yet  known. 
Some  change  is  produced  in  the  nerve,  which  is 
not  to  be  detected  in  any  way  excepting  by  its  effect 
at  the  farther  extremity.*  In  a  similar  manner,  a 
change  originating  in  a  nerve-cell  is  transmitted 
along  the  fiber  or  fibers  connected  with  it,  and 
manifests  itself  at  the  termination  of  the  fiber  in 
some  peculiar  manner.  Some  nerve-fibers  thus  con- 
vey impressions  from  the  outside  inward  to  the 
nerve-centers,  while  others  convey  them  from  the 
nerve-centers  outward  to  the  exterior  of  the  body. 
An  intelligible  illustration  of  this  is  to  be  seen  in 

*  It  has  been  found  by  the  use  of  delicate  instruments  (galvanom- 
eters) that  there  is  a  constant  electrical  current  in  all  nerves  in  a  state 
of  rest,  supposed  to  be  due  to  the  nutritive  changes  taking  place  in  the 
nerves.  When  the  nerve  is  stimulated,  however,  so  that  the  natural 
nerve-current  is  conveyed  along  the  nerve,  the  electrical  current  is  di- 
minished in  force. 


I/O 


ORGANS  OF  CO-ORDINATION. 


the  phenomena  of  ordinary  sensation  and  muscular 
contraction.  The  prick  of  a  pin  stimulates  the  ex- 
tremity of  a  nerve-fiber,  or  perhaps  of  several.  The 
current  originated  by  this  stimulus  travels  along 
the  course  of  the  nerve  to  the  nerve-center,  and 
produces  what  we  call  sensation.  Then  the  nerve- 
center,  acted  upon  by  this  stimulus,  sends  out  a 
certain  amount  of  nerve-force  along  another  nerve- 
fiber.  This  impulse  follows  the  course  of  the  nerve 
down  to  the  muscular  fiber  in  which  it  terminates, 
and  there  produces  contraction  of  the  muscle,  and 
removal  of  the  part  which  has  been  pricked,  out  of 
harm's  way.  This  process,  so  simple  to  describe, 
so  plain  in  its  gross  outline,  is  probably  a  very  com- 
plex one,  and  it  is  not  at  all  understood.  When  it 
takes  place,  as  it  often  does,  without  any  conscious- 
ness on  the  part  of  the  person,  it  is  called  reflex  ac- 
tion, because  the  result  of  the  first  stimulus,  which 
produced  the  sensation,  is  reflected,  as  it  were,  along 
the  second  nerve  to  the  muscle. 

216.  Rapidity  of  Nerve-Current. — It  seems,  at 
first  thought,  as  if  the  reaction  to  a  nervous  stimu- 
lus were  instantaneous.  If  the  finger  be  hurt,  it  is 
jerked  away  so  quickly  that  there  seems  to  be  no 
interval  between  the  injury  and  the  action.  And 
yet  it  is  evident  that,  if  the  received  theory  be  true, 
viz.,  that  a  current  must  go  from  the  finger  to  the 
brain  in  order  to  be  felt,  and  from  the  brain  back 
to  the  muscle  in  order  to  produce  muscular  con- 
traction, there  must  be  a  lapse  of  time.  Most  people 
would  probably  say,  however,  that  the  nerve-force 
must  travel  as  rapidly  as  electricity,  and  hence  the 
time  required  for  such  a  circuit  would  be  inappre- 
ciably short.     It  has  been  shown,  however,  by  in- 


NERVE-SUBSTANCE.  171 

genious  and  beautiful  experiments,  that  the  nerve- 
force  does  not  travel  over  one  hundred  and  ten 
feet  (thirty-three  metres)  per  second,  and  hence  to 
go  from  the  foot  to  the  brain  would  require  at  least 
one  twentieth  of  a  second,  and  the  same  to  return. 
Thus  an  injury  to  the  foot  would  not  be  followed 
by  voluntary  muscular  contraction  until  at  least 
one  tenth  of  a  second  had  elapsed.  Electricity,  on 
the  other  hand,  travels  with  almost  inconceivable 
rapidity. 

217.  Exhaustion  of  Nerves. — The  transmission 
of  an  impulse  along-  a  nerve-fiber  not  only  requires 
time,  but  exhausts  the  nerve.  We  have  previously 
shown  that  continued  muscular  contraction  exhausts 
the  muscular  fiber,  and  that  every  muscle  must  have 
rest  and  nourishment,  in  order  to  maintain  itself  in 
health  and  vigor.  It  is  the  same  with  the  nerves, 
but  they  recover,  when  exhausted,  much  more  slow- 
ly than  the  muscles,  and  require  a  longer  period  of 
rest. 

218.  Nerve-Fibers  as  Conductors  of  Force. — 
The  fact  that  nerve-fibers  are  mere  conductors  of 
nerve-force,  and  do  not  originate  it,  is  shown  by 
cutting  them  in  two.  All  sensation  and  motion 
then  cease  in  the  portion  of  the  body  supplied  by 
the  nerve  which  has  been  cut.  After  some  time, 
however,  such  injuries  become  healed,  the  cut  ex- 
tremities of  the  nerve  unite,  and  the  powers  of  sen- 
sation and  motion  return. 

219.  Gray  Matter  originates  Force. — It  has  been 
already  stated  that  the  gray  matter  originates  force. 
This  is  indicated  by  the  fact  that  all  the  nerve-fibers 
end  in  collections  of  gray  matter,  and  that  in  the 
natural  condition   no  nerve-fiber  conducts   an  im- 


i;2  ORGANS  OF  CO-ORDINATION. 

pulse  in  either  direction,  inward  or  outward,  un- 
less it  be  directly  connected  with  gray  matter. 
What  the  force  may  be  which  resides  in  the  nerve- 
cells,  and  what  changes  accompany  their  action, 
we  do  not  know,  and  possibly  never  shall  know. 
It  has  been  often  compared  to  electricity,  and  was 
once  supposed  to  be  identical  with  it,  but  it  has 
been  plainly  demonstrated  to  be  different.  The 
diminution  of  the  electrical  current  during  the  pas- 
sage of  the  natural  nerve-current  show^s  this,  and,  if 
a  nerve  be  tightly  bound,  the  transmission  of  the 
nervous  impulse  is  prevented,  while  the  electrical 
current  will  pass  through  the  constricted  nerve 
without  appearing  to  meet  with  resistance. 

220.  Difference  between  Cerebro-spinal  and 
Sympathetic  Nerves. — The  cerebro-spinal  nervous 
system  and  the  sympathetic  nervous  system  bear  a 
close  relation  to  the  voluntary  and  involuntary  mus- 
cular tissues  respectively.  The  voluntary  muscles 
are  supplied  by  nerves  from  the  cerebro-spinal  sys- 
tem, and  the  involuntary  muscles  by  the  sympathetic, 
and  the  same  differences,  that  we  have  observed 
between  the  two  kinds  of  muscular  tissue  in  their 
manner  of  contraction,  are  also  found  in  the  two 
systems  of  nerves.  A  stimulus  applied  to  any  por- 
tion of  the  cerebro-spinal  system  produces  an  im- 
mediate response,  while  irritation  of  any  portion  of 
the  sympathetic  system  only  produces  an  effect  after 
the  lapse  of  an  appreciable  time. 

The  only  portion  of  the  nervous  system  over 
which  we  have  any  control  whatever,  and  which 
stands  in  any  relation  to  our  consciousness,  is  the 
cerebro-spinal  system  (Fig.  53).  This  system,  con- 
stituting by  far  the  greater  bulk  of  our  nervous  ap- 


NER  VE-SUBSTANCE. 


173 


paratus,  comprises  the  brain  and  the  spinal  cord, 
together  with  all  the  nerves  which  take  their  origin 


Nerves  to 
left  arm. 


Nerves  to 
front  of 
left  leg. 

Nerves  to 
back  of 
left  leg. 


Nerves  to 
right  arm. 


Nerves  to 
front  of 
right  leg. 

Nerves  to 
back  of 
right  leg. 


Fig.  53. — Brain  and  spinal  cord,  with  the  thirty-one  pairs  of  spinal  nerves. 

in  these  organs.  The  brain  is  a  very  complex  or- 
gan, being  composed  of  several  different  ganglia, 
each  of  which  has  its  own  peculiar  functions.  In 
describing  the  nervous  system  it  will  be  convenient, 
therefore,  to  begin  with  the  sympathetic  system,  as 
being  the  simplest  in  its  structure  and  functions. 


CHAPTER   II. 

THE   SYMPATHETIC   SYSTEM. 

221.  Structure  of  the  Sympathetic  System. — The 
sympathetic  system  consists  of  a  double  chain  of 
nervous  ganglia,  running  from  one  extremity  of 
the  body  to  the  other,  not  including  the  limbs  (Fig. 
54).     The  arms  and  legs  are  organs  of  animal  life, 


Fig.  54. — The  sympathetic  system  of  nerves  in  the  trunk. 


THE  SYMPATHETIC  SYSTEM.  175 

and  are  supplied  with  cerebro-spinal  nerves.  The 
ganglia  of  the  sympathetic  vary  very  much  in  size, 
some  being  only  visible  with  the  microscope,  and 
others  as  large  as  a  pea,  or,  rarely,  even  larger. 
They  are  composed,  as  has  been  said,  of  gray  nerve- 
matter,  and  are  connected  with  each  other  and  with 
the  cerebro-spinal  nerves  by  means  of  communi- 
cating fibers.  Some  of  these  fibers  are  of  the  ordi- 
nary white  matter,  while  others  are  transparent  and 
grayish  in  color,  and  appear  to  consist  of  an  axis- 
cylinder  alone,  without  any  surrounding  myelin. 
The  sympathetic  ganglia  all  lie  very  deep  in  the 
cavities  of  the  body,  in  the  vicinity  of  and  sur- 
rounding the  important  organs,"*  whose  functions 
they  control,  and  it  is  very  difficult  to  get  at  them 
for  purposes  of  experiment.  The  consequence 
of  this  is,  that  very  little  has  been  learned  about 
the  real  action  of  the  sympathetic  system,  and 
many  of  its  functions  can  at  present  only  be  con- 
jectured. 

222.  Sluggish  Action  of  Sympathetic  Nerves. — 
The  sympathetic  nerves  have  been  proved  to  be 
capable  of  conveying  both  sensory  and  motor  im- 
pulses ;  but  these  properties  are  very  slow  in  mani- 
festing themselves,  in  marked  contrast  to  the  behav- 
ior of  the  cerebro-spinal  nerves.  If  the  extremity 
of  a  sympathetic  nerve  be  irritated,  it  is  only  after 
a  considerable  time  that  the  nervous  center  is  af- 

*  The  large  sympathetic  ganglia,  called  the  solar  plexus,  or  the 
semi-lunar  ganglia  (from  their  shape),  lying  behind  the  pit  of  the  stom- 
ach, constitute  what  has  been  sometimes  called  the  abdominal  brain. 
A  blow  in  this  region  is  very  dangerous,  for,  if  it  is  powerful  enough  to 
paralyze  these  ganglia  by  the  shock,  it  is  more  certain  to  cause  instant 
death  than  the  severest  blow  on  the  head. 


176  ORGANS  OF  CO-ORDINATION. 

fected,  and  the  reflex  motion  is  very  slow  in  its 
appearance.  This  fact  is  illustrated  in  the  inflam- 
mations and  congestions  of  internal  organs.  The 
sympathetic  system  mainly  furnishes  the  nervous 
supply  of  the  organs  of  digestion  and  secretion.  If 
any  irritation,  like  the  cold  air  of  a  draught  for  in- 
stance, affects  the  body,  the  result,  such  as  internal 
congestions,  etc.,  only  appear  after  some  time  has 
elapsed.  An  exposure  to  injurious  influences  may 
produce  a  serious  disease  through  the  sympathetic 
system,  and  yet  the  disease  may  not  declare  itself 
for  ten  or  fifteen  or  even  twenty-four  hours  after 
the  exposure. 

223.  Contraction  of  the  Pupil. — Various  familiar 
phenomena  show  this  sluggish  action  of  the  sympa- 
thetic nerves.  One  of  the  most  obvious  is  the  con- 
traction of  the  pupil  of  the  eye  under  exposure  to 
light.  When  a  strong  light  is  thrown  into  the  eye 
the  pupil  grows  smaller  and  shuts  out  the  excess  of 
light.  On  the  other  hand,  when  the  supply  of  light 
is  diminished,  the  pupil  enlarges  so  as  to  admit 
more.  Now,  these  changes  in  the  size  of  the  pupil 
take  place  very  slowly.  When  we  go  from  a  light 
room  into  a  dark  one  it  is  several  seconds,  some- 
times a  minute,  before  we  can  see  anything,  simply 
because  the  pupil  does  not  admit  enough  light  and 
requires  time  to  enlarge  sufficiently.  When  we  go 
from  a  dark  room  to  a  very  light  one  we  are  daz- 
zled ;  the  pupil  is  too  large  and  admits  too  much 
light,  and  we  are  obliged  to  shade  our  eyes  until 
contraction  has  taken  place.  These  phenomena  are 
the  result  of  impressions  made  on  the  sympathetic 
system,  and  serve  as  an  excellent  illustration  of  the 
slowness  and  precision  of  its  action,  as  well  as  of  the 


THE  SYMPATHETIC  SYSTEM. 


177 


fact  that  its  functions  are  entirely  beyond  our  con- 
scious control.* 

224.  Effect  of  dividing  a  Sympathetic  Nerve. — 
One  of  the  most  remarkable  facts  relating  to  the 
sympathetic  system  was  discovered  by  the  cele- 
brated physiologist,  Bernard,  by  the  following  ex- 
periment :  The  rabbit's  ear  is  large  and  well  sup- 
plied with  blood-vessels,  and  is  covered  with  a  thin, 
transparent  skin,  which  allows  all  changes  under- 
neath it  to  be  easily  seen.  If,  now,  the  sympathetic 
nerve  running  to  the  ear  be  divided,  the  ear  be- 
comes red  and  hot,  and  the  blood-vessels  are  seen 
to  be  enlarged  and  much  fuller  of  blood  than  they 
usually  are.  There  is  no  stagnation  of  the  circula- 
tion, and,  after  the  lapse  of  a  sufficient  time,  three 
or  four  weeks,  the  divided  ends  of  the  nerve  unite 
and  the  ear  returns  to  its  natural  condition.  If, 
after  the  nerve  has  been  divided,  as  above,  while 
the  ear  is  in  its  red  and  hot  condition,  the  end  of 
the  nerve  nearest  the  ear  be  irritated  by  a  galvanic 
current,  the  blood-vessels  contract,  the  unusual 
amount  of  blood  is  expelled  from  them,  and  the  ear 
resumes  its  ordinary  temperature  and  color.  If  the 
cause  of  irritation  be  removed,  the  redness  and  heat 
return.  These  facts  seemed  to  indicate  that  the 
supply  of  blood  in  a  part  was  regulated  by  the  sym- 
pathetic system  of  nerves,  a  supposition  which  was 
confirmed  by  further  experiments. 

*  The  iris,  i.  e.,  the  muscular  curtain  surrounding  the  pupil,  is  sup- 
plied with  nerves  from  the  cerebro-spinal  system  as  well  as  from  the 
sympathetic.  The  relative  functions  of  the  two  sets  of  fibers  are  not 
well  understood,  but  the  sluggish  and  involuntary  character  of  the 
changes  in  the  size  of  the  pupil  shows  that  the  influence  of  the  sympa- 
thetic nerves  predominates. 


178  ORGANS  OF  CO-ORDINATION. 

225.  Influence  of  the  Sympathetic  Nerves  on  Se- 
cretion.— lie  found  that,  if  the  sympathetic  nerve 
supplying  any  of  the  glands  in  the  body  be  divided, 
an  increased  supply  of  blood  takes  place  and  in- 
creased secretion  by  the  gland  follows.  If  the  pa- 
rotid gland  be  treated  in  this  way,  an  increased  flow 
of  saliva  takes  place.  The  same  effect  is  also  pro- 
duced on  this  gland  by  galvanic  irritation  of  the 
nerve  of  taste.  Any  savory  substance  in  the  mouth, 
then,  irritating  the  nerve  of  taste,  gives  rise  to  a  re- 
flex action  through  the  sympathetic  nerve  which 
goes  to  the  parotid  gland  and  produces  a  flow  of 
saliva.  This  is  what  we  call  "  feeling  the  mouth 
water."  The  same  effect  may  even  be  produced  by 
purely  emotional  causes,  as  the  mere  sight  of  an 
appetizing  article  of  food. 

226.  Effect  of  Emotion  on  the  Sympathetic 
Nerves. — Blushing  is  another  phenomenon  depend- 
ing on  the  control  of  the  sympathetic  nerves  over 
the  blood-vessels.  The  emotion  of  shame  produces 
a  temporary  paralysis  of  the  sympathetic  nerves, 
and  gives  rise  to  the  same  effects  as  a  division  of  the 
nerve.  Blood  rushes  to  the  superficial  blood-vessels 
and  they  become  redder  and  hotter  than  they  ordi- 
narily are.  The  blush  is  more  evident  in  the  cheeks 
than  elsewhere,  because  the  skin  is  thinner  there, 
and  the  blood-vessels  more  numerous  ;  but  the 
blush  extends,  in  reality,  much  more  widely  than  is 
commonly  supposed,  and  covers  a  large  portion  of 
the  surface  of  the  body.  The  peculiar  character- 
istics of  the  sympathetic  system  are  to  be  plainly 
discerned  in  the  blush.  It  is  not  instantaneous,  but 
comes  on  slowly  after  an  indignity,  gradually  rises 
to  its   greatest   height,  and  then  gradually  disap- 


THE  SYMPATHETIC  SYSTEM. 


179 


pears.  It  is  also  beyond  the  control  of  the  will. 
If  a  person  really  feels  the  emotion,  he  can  not  re- 
strain the  blush.  The  only  means  of  preventing  it 
lies  in  such  a  constant  schooling  of  the  mind  that 
feelings  of  shame,  modesty,  insulted  dignity,  etc., 
shall  not  be  felt.  When  a  person  has  arrived  at 
this  point  of  self-control  he  will  not  blush.  But  who 
would  wish  to  purchase  exemption  at  such  a  price  ? 
Many  persons  are  ashamed  of  blushing,  but  who 
would  be  ashamed  of  being  ashamed  ?  The  two 
can  not  be  separated,  and  one  who  has  lost  the  sense 
of  shame  entirely  has  lost  much  of  what  commends 
us  to  the  sympathy  and  respect  of  our  fellows. 

227.  The  Vaso-motor  Nerves.  —  The  nerves 
which  thus  control  the  supply  of  blood  to  the 
blood-vessels  are  called  the  vaso-motor  nerves.  They 
have  been  already  referred  to  in  another  part  of 
this  book.  They  have  received  the  name  of  vaso- 
motor because  they  control  the  motion  of  the  walls 
of  the  vessels  (vasa)  producing  contraction  or  relax- 
ation. Although  they  are  chiefly  of  the  sympa- 
thetic system,  they  receive  fibers  from  the  cerebro- 
spinal system.  The  two  systems  are  not  entirely 
distinct  from  each  other,  but  there  are  certain  func- 
tions in  which  they  are  so  widely  different  that  we 
can  say  with  certainty  this  action  belongs  to  the 
cerebro-spinal  system,  or  that  one  to  the  sympa- 
thetic ;  Avhile  between  these  extremes  are  all  sorts 
of  gradations,  so  that  in  many  cases  we  are  unable 
to  distinguish  the  characteristics  of  either  system, 
and  must  say  of  them  that  we  do  not  know  how 
they  are  produced  or  that  both  systems  probably 
unite  their  functions. 

228.  Influence  of  the  Sympathetic  System  on  Di- 


^o  ORGANS  OF  CO-ORDINATION. 

gestion. — The  whole  process  of  digestion  is  presided 
over  and  regulated  by  the  sympathetic  nervous  sys- 
tem. The  introduction  of  food  into  the  stomach 
stimulates  the  nervous  ganglia  in  the  abdomen,  and 
through  their  influence  is  followed  by  all  the  phe- 
nomena of  secretion,  muscular  movements,  and  ab- 
sorption, which  have  been  shown  to  accompany 
and  form  a  part  of  the  process  of  digestion.  All  of 
these  phenomena  are  beyond  our  control,  but,  as 
has  been  shown  in  the  case  of  the  blush,  the  nervous 
supply  of  the  sympathetic  is  favorably  or  unfavor- 
ably affected  by  strong  emotions.  And  it  is  through 
these  ganglia  and  their  connections  that  anger,  fear, 
or  other  depressing  emotions,  produce  such  an  in- 
jurious effect  on  the  digestive  organs  during  and 
after  a  meal. 

229.  Effect  of  Cold  on  the  Sympathetic  System. — 
It  is  through  the  reflex  action  of  these  nerves,  also, 
that  haemorrhage  can  often  be  checked  by  the  ap- 
plication of  cold,  and  that  inflammation  of  internal 
organs  may  result  from  the  same  cause.  The  mu- 
cous membranes,  for  the  same  reason,  seem  to  be 
more  exposed  to  such  inflammations  than  any  other 
portion  of  the  organism.  Hence,  exposure  to  a  cold 
draught  is  very  apt  to  bring  on  such  a  disorder.  In 
one  person  it  may  affect  one  mucous  membrane,  in 
another  another,  according  to  the  relative  condition 
of  the  membranes  at  the  moment.  After  such  an 
exposure,  one  person  may  have  a  severe  cold  in  the 
head,  another  a  bronchitis,  another  a  sore  throat, 
another  a  diarrhoea  or  inflammation  of  the  mucous 
membrane  of  the  intestines.*     All  of  these  results 

*  Many  persons,  instead  of  catching  cold  in  the  nose  or  throat  after 
exposure,  have  their  bowels  affected,  and  the  resulting  catarrh  causes  a 


THE  SYMPATHETIC  SYSTEM.  181 

are  beyond  our  control,  and  the  only  way  to  pre- 
vent them  is  to  keep  out  of  danger.  When  a  person 
is  in  health,  food  introduced  into  the  stomach  will 
inevitably  be  digested,  whether  he  wills  it  or  not, 
and,  if  he  undergoes  certain  exposures,  he  will  take 
cold,  in  like  manner,  whether  he  wills  it  or  not.* 

230.  Exhaustion  of  the  Sympathetic  System. — 
As  the  sympathetic  system  is  so  intimately  con- 
nected with  the  processes  of  nutrition,  and  indeed 
with  all  the  functions  of  those  organs  which  main- 
tain us  in  life,  without  our  consciousness,  it  is  evi- 
dent that  it  should  be  well  taken  care  of  and  nothing 
done  to  cripple  it.  We  have,  then,  to  bear  in  mind 
that  nerves  require  rest  as  well  as  any  other  part  of 
the  body,  that  they  easily  become  exhausted,  and 
that  they  require  a  longer  period  for  recuperation 
than  the  muscles  do.  The  surest  sign,  perhaps,  of 
exhaustion  of  the  sympathetic  system  will  be  found 

diarrhoea.  When  a  person  is  specially  liable  to  this  affection,  he  should 
wear  a  thick  flannel  bandage  around  the  abdomen,  which  will  furnish 
almost  entire  relief  from  such  attacks. 

*  A  cold  is  generally  the  result  of  the  sudden  chilling  of  some  part 
or  the  whole  of  the  surface  of  the  body.  The  first  effect  of  such  a  chill 
is  to  contract  the  blood-vessels  on  the  surface  and  overfill  those  that  lie 
deeper,  and  thus  to  cause  congestions  of  the  internal  organs.  Such  an  ef- 
fect seems  to  be  especially  apt  to  follow  a  cold  draught  striking  the  back 
of  the  head  or  neck  or  the  ankles.  Now,  active  muscular  exercise  tends 
to  drive  the  blood  to  the  surface,  and  is  therefore  a  natural  preventive 
of  colds.  It  tends  to  keep  the  blood  at  the  surface,  where  a  conges- 
tion will  be  relieved  by  perspiration,  and  prevents  its  accumulation  in 
the  deeper  organs,  where  it  is  more  likely  to  cause  trouble.  If  expos- 
ure to  cold,  therefore,  can  not  be  avoided,  we  must  keep  up  a  brisk 
circulation  by  physical  exercise.  Wet  clothing  should  be  changed  for 
dry  as  soon  as  possible,  for  so  long  as  it  remains  in  contact  with  the 
body  it  absorbs  a  great  amount  of  heat  from  it  and  keeps  up  a  constant 
chilling  of  the  surface.  When  a  person  is  not  engaged  in  physical  ex- 
ertion, he  should  avoid  draughts. 
9 


1 82  ORGANS  OF  CO-ORDINATION. 

in  failure  of  nutrition.  If  a  person  grows  thin  and 
pale  and  languid,  notwithstanding  a  good  supply 
of  food,  or  if  his  food  be  not  appropriated  by  the 
body — in  short,  if  his  nutrition  become  impaired, 
and  no  organic  disease  be  discoverable — it  is  prob- 
ably the  result  of  nervous  exhaustion,  and  means 
should  be  taken  to  relieve  the  overtasked  organs. 
Rest  will  accomplish  wonders  in  many  cases  of  ill- 
ness, especially  where  there  is  no  disease  of  any 
particular  organ  to  be  detected. 


CHAPTER   III. 

THE    SPINAL    CORD. 

231.  Structure  of  the  Spinal  Cord. — The  spinal 
cord  is  that  portion  of  the  nervous  system  which 
lies  within  the  spinal  canal.  It  extends  from  the 
junction  of  the  spinal  column  with  the  skull,  down 
to  the  loins,  and  is  about  a  foot  and  a  half  long  and 
a  little  less  than  half  an  inch  in  diameter.  It  weighs 
about  an  ounce  and  a  half.  It  does  not  occupy  the 
whole  spinal  canal,  but  the  space  around  it  is  filled 
with  membrane,  blood-vessels,  and  nerves.  At  its 
upper  extremity  it  passes  into  the  brain,  and  at  its 
lower,  just  below  the  last  rib,  it  divides  into  a  bundle 
of  small  nerves,  presenting  very  much  the  appear- 
ance of  a  tassel  at  the  end  of  a  thick  cord.* 

The  spinal  cord  consists  partly  of  white  and 
partly  of  gray  matter.  The  gray  portion  occupies 
the  central  portion  of  the  cord,  and  is  arranged 
somewhat  in  the  form  of  the  letter  H,  with  the  two 
upright  marks  curving  outward  at  both  ends  (Fig. 
55).  The  remainder  of  the  cord,  in  which  this  gray 
substance  is  imbedded,  is  composed  of  white  matter. 

The  spinal  cord,  throughout  its  whole  length,  is 
divided  by  fissures,  one  of  which  extends  from  be- 

*  This  part  of  the  spinal  cord  is  called  the  caud'a  equina — i.  e.,  the 
horse's  tail,  which  it  somewhat  resembles. 


^4  ORGANS  OF  CO-ORDINATION. 

fore  backward,  and  the  other  from  behind  forward, 
the  two  nearly  meeting.  They  are,  however,  sepa- 
rated, and  the  halves  of  the  cord  kept  in  communi- 
cation by  a  bridge  of  gray  matter,  which  passes  over 
from  one  to  the  other,  forming  the  cross-line  of  the 
letter  H. 

232.  The  Spinal  Nerves. — The  spinal  cord  sends 
out  nerves  through  its  whole  course.  With  the  ex- 
ception of  the  head  and  face,  all  the  muscles  and  the 
skin  of  the  body  receive  their  nervous  supply  from 
this  source.  These  nerves,  thirty-one  pairs  in  all, 
issue  from  the  spinal  column  between  the  vertebrae 
through  small  openings. 

233.  Properties  of  the  Spinal  Nerves. — All  parts 
of  the  body,  which  are  supplied  with  spinal  nerves, 
are  endowed  with  two  remarkable  properties,  Sen- 
sation and  motion.  As  long  as  the  nervous  supply 
remains  in  a  natural  and  healthy  condition,  any  por- 
tion of  the  body  feels,  and  any  portion  can  be  moved 
from  one  place  to  another.  These  movements  are 
sometimes  voluntary  and  sometimes  we  are  entirely 
unconscious  of  them,  and  it  is  only  within  a  few 
years  that  physiology  has  been  able  to  offer  any  ex- 
planation whatever  of  these  facts. 

234.  Sensation  and  Motion. — When  we  consider 
attentively  the  property  of  sensation,  we  find  that 
there  are  two  great  divisions  of  it,  easily  distin- 
guishable and  easily  demonstrated,  viz.,  sensibility 
to  pain  and  ordinary  sensation.  When  a  person  is 
brought  under  the  influence  of  an  anaesthetic,  the 
sensibility  to  pain  disappears  before  ordinary  sen- 
sation is  lost,  and  even  while  the  individual  is  still 
conscious.  In  slight  surgical  operations  this  fact 
is  often  strikingly  manifest.    A  tooth  may  be  pulled, 


THE  SPINAL   CORD.  ^5 

and  the  patient  be  conscious  of  every  step  of  the 
proceeding,  without  feeling  the  slightest  pain.  Nar- 
cotics, too,  may  relieve  the  pain  of  a  neuralgia, 
while  the  person  who  has  taken  them  remains  per- 
fectly in  possession  of  his  senses.  Physiologists 
have  made  other  discriminations  of  sensation,  which 
it  is  not  necessary  to  mention  here. 

The  phenomena  of  motion  are  familiar,  and  re- 
quire no  separate  consideration. 

235.  Effect  of  dividing  a  Nerve. — If  one  of  the 
spinal  nerves  be  cut  in  two,  sensation  and  motion 
are  abolished  in  the  portion  of  the  body  supplied 
by  that  nerve.  This  shows  that  sensation  and  mo- 
tion are  both  conveyed  in  the  same  nerve.  But 
here  a  difficulty  arises.  Sensation  implies  the  pas- 
sage of  a  nerve-current  from  without  inward,  to- 
ward a  nerve-center;  whereas  motion  implies  the 
passage  of  a  current  from  within  outward,  from  the 
nerve-center  to  the  muscle.  Can  both  these  cur- 
rents be  transmitted  at  the  same  time,  or  can  the 
axis-cylinder  of  the  nerve-fiber  be  used  for  the  pas- 
sage of  the  nerve-current  in  either  direction  accord- 
ing to  circumstances  ?  This  is  the  problem  which 
waited  until  this  century  to  be  solved.  The  sim- 
plest explanation  has  been  found  to  be  the  correct 
one.  As  every  nerve  is  made  up  of  many  fibers,  it 
would  be  natural  to  suppose  that  some  of  these 
fibers  might  serve  as  conductors  of  sensation,  and 
others  of  motion.  This  was  made  all  the  more 
probable  by  the  fact  that,  in  many  forms  of  dis- 
ease, it  was  seen  that  the  power  of  sensation  might 
be  abolished,  while  that  of  motion  remained  ;  or,  on 
the  other  hand,  the  power  of  motion  might  be  par- 
alyzed, while  that  of  sensation  remained  unimpaired. 


1 86  ORGANS  OF  CO-ORDINATION. 

And,  in  fact,  the  above  explanation  of  these  phe- 
nomena was  found  to  be  correct.  The  first  who 
demonstrated  this  appears  to  have  been  Sir  Charles 
Bell,*  although  Magendief  has  strong  counter- 
claims to  the  honor.  The  experiments  by  which 
the  truth  was  established  were  decisive,  and  have 
been  often  repeated  by  other  physiologists.  They 
are  the  following : 

236.  The  Roots  of  the  Spinal  Nerves. — The  spi- 
nal nerves  do  not  take  their  origin  from  the  spinal 
cord  as  single  trunks,  but  each  one  arises  by  two 
roots.  One  of  these  roots  is  formed  of  fibers  com- 
ing from  the  anterior  portion  of  the  cord,  and  is 
called  the  anterior  root ;  the  other  is  formed  by 
fibers  from  the  posterior  portion  of  the  cord,  and 
is  called  the  posterior  root ;  the  latter,  at  a  short  dis- 
tance from  its  source,  passes  through  a  small  gan- 
glion of  gray  matter.  These  two  roots,  anterior 
and  posterior,  approach  each  other  and  unite  in  a 
single  cord  just  before  leaving  the  spinal  canal. 
This  cord,  therefore,  contains  fibers  from  both  por- 
tions of  the  spinal  cord,  and,  after  running  a  short 
distance,  it  again  divides  into  two  nervous  trunks, 
one  of  which  supplies  the  front  of  the  body  and  the 
other  the  back. 

The  experiments  referred  to  consisted  in  divid- 
ing, not  the  nerves,  but  the  anterior  and  posterior 
roots  of  the  nerves,  inside  the  spinal  canal,  in  a  liv- 

*  Sir  Charles  Bell,  a  distinguished  Scotch  anatomist,  physiologist, 
and  surgeon  (1774-1842),  Professor  of  Surgery  in  the  University  of 
Edinburgh. 

f  Francois  Magendie,  a  celebrated  French  physiologist  (1783-1855), 
Professor  of  Anatomy  in  the  College  of  France,  especially  well  known 
for  his  experiments  on  living  animals. 


THE  SPINAL   CORD.  i%y 

ing  animal,  and  watching-  the  result.  Severe  and 
painful  as  these  experiments  were,  and  however  ob- 
jectionable from  the  animal-lover's  point  of  view, 
they  have  probably  done  more  to  explain  the  mys- 
teries of  the  nervous  system,  and  to  give  a  fresh  im- 
pulse to  investigation  on  the  most  interesting  and 
important  subject  with  which  man  can  occupy  him- 
self, than  any  similar  experiments  in  the  world's 
history,  if  we  except  those  which  demonstrated  the 
circulation  of  the  blood. 

237.  Division  of  the  Anterior  Root. — When  the 
anterior  root  of  a  spinal  nerve  is  divided  (Fig.  55), 
the  portion  of  the  body  supplied  by  the  nerve  of 


*ICR  ROOT 


Fig.  55. — Cross  section  of  spinal  cord  and  roots  of  spinal  nerves,  with  ante- 
rior root  cut. 

which  this  particular  root  forms  a  part,  loses  its 
power  of  motion,  but  preserves  its  sensibility  unim- 
paired. If  the  portion  of  the  body  supplied  by  this 
nerve  be  pinched  or  pricked,  the  animal  gives  evi- 
dent signs  of  pain,  and  endeavors  to  get  out  of  the 
way  of  the  irritation,  but  is  utterly  unable  to  move 
the  muscles  of  the  part.  If,  now,  the  ends  of  the  cut 
nerve  be  irritated,  the  following  results  are  obtained : 
On  irritation  of  the  end  nearest  the  part  supplied 
by  the  nerve,  the  muscles  of  that  part  become  strong- 
ly contracted,  or  convulsed,  while  the  animal  gives 
no  indication  of  feeling  anything  whatever.  If  the 
end  nearest  the  spinal  cord  be  irritated,  no  effect 


1 88  ORGANS  OF  CO-ORDINATION. 

whatever  is  produced.  There  are  no  convulsive 
movements  of  the  muscles,  and  no  indication  of  sen- 
sation. This  seems  to  show  that,  in  the  fibers  of 
the  anterior  root,  the  nervous  impulse  is  transmit- 
ted from  within  outward,  and  gives  rise  to  the  phe- 
nomena of  motion,  while  they  have  nothing  to  do 
with  sensation. 

238.  Division  of  the  Posterior  Root. — If,  now, 
instead  of  dividing  the  anterior  root,  we  divide  the 
posterior  (Fig.  56),  we  find  that  the  part  supplied  by 
the  nerve  has  lost  sensation,  but  retains  the  power 


Fig.  56. — Cross  section  of  spinal  cord  and  roots  of  spinal  nerves,  with  pos- 
terior root  cut. 

of  motion.  If  it  be  pinched,  pricked,  or  injured  in 
any  way,  no  effect  is  produced,  and  the  animal  ap- 
pears to  take  no  notice  of  it  whatever.  This  shows 
that  sensation  in  the  part  is  abolished.  If,  now,  the 
cut  ends  of  the  root  be  irritated,  we  find  the  follow- 
ing results  :  On  irritation  of  the  end  nearest  the  part 
no  effect  whatever  is  produced.  If,  on  the  other 
hand,  the  end  nearest  the  cord  be  irritated,  the  ani- 
mal utters  cries  of  pain,  and  moves  the  muscles  sup- 
plied by  the  nerve  which  has  been  operated  on,  in 
endeavors  to  escape.  This  shows  that  the  power 
of  motion  has  not  been  interfered  with  by  the  oper- 
ation, and  it  also  shows  that,  in  the  posterior  roots  of 
the  spinal  nerves,  the  nervous  impulse  is  transmitted 
from  without  inward,  and  has  to  do  with  sensation. 


THE  SPINAL    CORD.  189 

239.  Two  Kinds  of  Fibers  in  Each  Nerve. — The 

anterior  roots,  then,  are  composed  of  motor  fibers, 
and  the  posterior  roots  of  sensory  fibers.  The  two 
unite,  as  has  been  shown,  to  form  a  single  cord, 
which  afterward  divides  again  to  supply  the  front 
and  back  of  the  body.  Every  spinal  nerve  in  this 
way  is  made  up  of  both  sensory  and  motor  fibers, 
or  fibers  which  convey  sensation  and  fibers  which 
convey  motion ;  and  thus,  from  the  constitution  of 
the  nerve,  it  is  easy  to  see  how  the  powers  of  sen- 
sation or  motion  can  be  abolished  separately,  one 
remaining  intact  while  the  other  disappears. 

240.  Relation  of  the  Spinal  Cord  to  the  Brain. — 
These  properties  of  sensation  and  motion  have  been 
considered  only  in  their  relations  to  consciousness. 
The  sensations  have  been  spoken  of  as  felt  by  the 
animal,  and  the  movements  as  voluntary.  In  order 
for  this  to  be  so,  there  must  be  some  connection  be- 
tween the  nerves  and  the  brain,  for  consciousness 
has  its  seat  in  the  latter,  as  we  shall  hereafter  see. 
And  in  fact  it  has  been  proved  that  the  nerve-fibers, 
after  entering  the  spinal  cord,  pass  upward  in  its 
interior  toward  the  brain.  It  is  probable  that  the 
white  matter  of  the  cord  is  largely  composed  of 
fibers  which  connect  the  brain  in  this  way  with  the 
exterior  of  the  body. 

As  the  nerve-fibers  approach  the  brain,  however, 
at  the  very  summit  or  upper  extremity  of  the  spi- 
nal cord,  they  cross  over  from  one  side  of  the  cord 
to  the  other,  the  fibers  from  the  right  side  passing 
over  to  the  left,  and  those  from  the  left  going  over 
to  the  right.  The  crossing  of  the  motor  fibers  only 
takes  place  at  this  point,  while  the  sensitive  fibers 
cross  to  the   opposite  side  of  the  cord  soon  after 


190 


ORGANS  OF  CO-ORDINATION. 


joining  it.  The  consequence  of  these  facts  is,  that 
the  right  side  of  the  body  comes  into  direct  com- 
munication with  the  left  side  of  the  brain,  and  the 
left  side  with  the  right  brain.  An  injury  to  the 
brain,  therefore,  on  either  side,  produces  paralysis 
of  the  opposite  side  of  the  body.  An  apoplexy* 
affecting  the  right  side  of  the  brain  brings  on  paraly- 
sis of  the  left  side  of  the  body  ;  and  conversely,  if  we 
see  a  person  whose  left  side  is  paralyzed,  we  look 
for  the  injury  which  has  caused  it  on  the  right  side 
of  the  head. 

241.  Sensations  referred  to  Extremity  of  Nerve. 
— It  has  already  been  said  that  the  nerve-fibers  act 
merely  as  conductors  of  an  impulse,  and  do  not 
themselves  originate  nervous  force.  In  consequence 
of  this,  an  injury  to  any  portion  of  a  nerve  always 
produces  the  same  effect  as  if  it  were  at  its  extrem- 
ity. The  pain  which  results  from  any  impression 
on  a  nerve-fiber  is  always  referred  by  the  nerve- 
center  which  receives  it  to  the  termination  of  that 
particular  nerve.  And  this  fact  clearly  explains 
many  things  that  once  were  not  understood.  The 
ulnar  nerve  furnishes  a  good  illustration  of  this.  At 
the  inside  of  the  back  of  the  elbow  are  two  bony 
projections,  with  a  hollow  canal  between  them.  At 
the  bottom  of  this  canal,  not  far  below  the  skin,  runs 
a  large  nerve  called  the  ulnar  nerve,  because  it  sup- 
plies the  ulnar  side  of  the  fore-arm  and  hand.  If 
this  nerve  be  pressed  or  injured  in  any  way,  a  tin- 
gling sensation  is  felt  in  the  little  finger  and  the  ad- 

*  Apoplexy,  from  the  Greek,  meaning  a  sudden  stroke.  It  is  caused 
by  the  giving  way  of  some  blood-vessel  in  the  brain,  and  the  blood 
escaping  into,  compressing,  and  tearing  apart  the  delicate  nerve-tissue, 
causes  paralysis  and  often  entire  unconsciousness,  or  death. 


THE  SPINAL   CORD. 


191 


joining  side  of  the  ring-finger,  the  parts  supplied  by 
this  nerve.*  Striking  examples  of  the  same  phe- 
nomenon are  often  seen  in  persons  who  have  lost 
limbs  by  amputation.  If  the  end  of  the  nerve  which 
remains  in  the  stump  be  irritated  in  any  way,  as  by 
the  contraction  of  the  scar,  the  person  feels  the  irri- 
tation precisely  as  if  it  were  in  the  lost  limb.  If  any 
person's  arm  were  cut  off,  for  instance,  just  below 
the  elbow,  and  the  stump  of  the  ulnar  nerve  were 
irritated,  he  would  feel  the  tingling  sensation  in  the 
little  and  ring  fingers  of  his  hand  just  as  much  as  if 
the  hand  were  still  attached  to  the  arm.  The  sen- 
sation is  precisely  the  same,  and  can  only  be  cor- 
rected by  the  sense  of  sight  or  by  the  individual's 
own  memory  or  reason.  It  is  this  fact  which  has 
given  rise  to  the  numerous  accounts  of  persons  who 
have  felt  people  maltreating  their  amputated  limbs, 
when  they  perhaps  were  already  decayed,  or  were 
hundreds  of  miles  away. 

242.  Reflex  Action  of  the  Spinal  Cord. — All  the 
phenomena  which  have  been  described  might  occur 
just  as  well  if  the  spinal  cord  were  merely  a  large 
bundle  of  white  fibers  running  down  from  the  brain, 
and  sending  out  branches  to  different  parts  of  the 
body.  It  has,  however,  a  considerable  amount  of 
gray  nerve-matter  in  its  interior,  and,  as  we  have 
seen  that  this  form  of  nerve-matter  originates  force, 
we  are  prepared  to  infer  that  the  spinal  cord  can 

*  The  ulnar  nerve  supplies  the  little  finger,  the  adjoining  side  of 
the  ring-finger,  and  that  side  of  the  hand  as  far  as  the  wrist.  Pressure 
upon  it,  therefore,  interferes  with  the  nervous  supply  of  those  parts, 
and  they  tingle  and  become  numb.  The  queerness  of  the  sensation 
produced  has  caused  this  nerve  to  be  commonly  known  as  the  crazy- 
bone,  or  the  funny-bone,  although  it  is  not  a  bone  at  all. 


I92  ORGANS  OF  CO-ORDINATION. 

originate  movements  and  receive  sensations  without 
any  connection  with  or  dependence  on  the  brain. 
And  this  is  found  actually  to  be  the  case.  If  the 
head  of  a  frog  be  cut  entirely  off,  leaving  the  body 
otherwise  uninjured,  sensation  and  motion  are  still 
manifested  in  the  trunk  and  limbs.  If  the  toe  be 
pinched,  the  leg  will  be  drawn  up  out  of  the  way. 
This  is  the  same  effect  that  is  produced  when  the 
animal  is  entire,  with  this  exception :  there  is  no 
attempt  to  escape  from  further  injury.  In  other 
words,  there  is  no  brain-action,  no  reasoning.  The 
irritation  sends  a  nerve-current  along  the  sensory 
nerve  to  the  spinal  cord.  There  it  produces  cer- 
tain changes  in  the  cells  of  the  gray  matter,  and 
from  them  another  current  is  sent  outward  along 
the  motor  nerve  to  the  muscles,  and  movement  re- 
sults. If  the  nerve  be  severed,  no  such  effect  can 
be  produced.  If  the  spinal  cord  be  destroyed,  the 
nerves  remaining  intact,  no  such  effect  will  occur. 
These  facts  show  that  the  cord  itself  has  the  prop- 
erty of  receiving  sensations  and  sending  out  motor 
impulses.  This  action  of  the  spinal  cord,  by  which 
it  produces  a  movement  in  response  to  and  in  con- 
sequence of  a  sensation,  is  called  reflex  action. 

243.  Diseases  of  the  Spinal  Cord. — Experiments 
like  the  above,  of  course,  can  not  be  performed  on 
human  beings,  but  the  course  of  nature  often  per- 
forms them  for  us.  Diseases  are  not  uncommon  in 
which  the  spinal  cord  is  completely  cut  across  in 
some  portion  of  its  length,  so  that  there  is  no  nerv- 
ous communication  between  the  brain  and  that  part 
of  the  body  below  the  seat  of  disease  or  injury. 
In  such  cases  we  have  paralysis  of  the  kind  called 
by  physicians  paraplegia — i.  e.,  the  lower  portion  of 


THE  SPINAL   CORD. 


193 


the  body  is  no  longer  under  control  of  the  brain, 
and  no  longer  capable  of  voluntary  movements.  It 
is  also  entirely  beyond  the  domain  of  consciousness; 
injuries  to  the  paralyzed  part  cause  no  sensation  in 
the  brain.  The  separation  of  such  a  part  of  the 
body  from  all  relation  to  consciousness,  whether  of 
sensation  or  of  motion,  is  as  complete  as  if  it  formed 
part  of  another  body.  Notwithstanding  this  fact, 
we  often  find  the  spinal  cord  below  the  seat  of  inju- 
ry to  be  in  the  same  condition  as  that  of  the  decapi- 
tated frog.  If  the  disease  or  injury  has  been  con- 
fined to  a  particular  part  of  the  cord,  and  the  portion 
below,  with  its  nerves,  be  still  in  a  healthy  condition, 
excepting  that  it  is  separated  from  the  brain,  a  stim- 
ulus applied  to  any  of  the  nerves  will  produce  a 
response  which  is  immediate  and  decided.  A  person 
in  this  condition  looks  on  and  sees  his  feet  pinched, 
or  pricked,  or  burned,  and  sees  the  irritation  followed 
by  violent  convulsive  kicks  and  thrusts  of  the  limbs, 
without  the  slightest  knowledge  of  what  is  going  on, 
excepting  what  he  receives  through  the  sense  of  sight. 
244.  Automatic  Actions. — Certain  actions,  which 
are  at  first  voluntary,  and  only  accomplished  by  great 
effort,  become,  after  a  time,  so  natural  and  easy,  that 
they  seem  to  be  carried  on  unconsciously,  through 
the  action  of  the  spinal  cord.  Thus,  in  the  act  of 
walking,  a  harmonious  action  of  several  muscles  is 
required  to  keep  the  balance,  an  action  wThich  is 
at  first  learned  only  after  prolonged  and  incessant 
effort.  In  after-life  it  becomes  so  easy  as  to  be 
carried  out  without  consciousness,  as  has  been  often 
shown  in  the  case  of  soldiers,  who  have  continued 
to  walk  in  the  ranks  and  keep  up  with  their  com- 
rades on  the  march  while  fast  asleep. 


CHAPTER   IV. 


THE    BRAIN. 


245.  The  Brain. — The  brain  and  the  cerebrum  are 
often  spoken  of  as  if  they  were  convertible  terms. 
But  this  is  not  correct.  The  brain  includes  all  that 
part  of  the  nervous  system  which  lies  within  the  cav- 
ity of  the  skull.  This  great  mass  of  nervous  matter 
is  made  up  of  several  distinct  ganglia,  which,  to  be 

sure,  are  connected  with 
one  another  and  interde- 
pendent, and  yet  each  of 
them  has  its  own  particular 
function  which  the  others 
have  not  (Fig.  57).  The  cere- 
brum is  merely  one  of  these 
ganglia,  and,  although  the 
highest  in  the  scale  as  re- 
gards the  character  of  its 
functions,  it  being  the  gan- 
glion      which      principally 

Fig.  57. — Diagram  showing  the        .  .  . 

position  of  the  nervous  cen-  gives  man  his  pre-eminence 
ters  in  the  head.  over  the  lower  animals,  it  is 

one  of  the  least  important 
as  regards  the  mere  preservation  of  life.  In  many 
of  the  lower  animals  it  can  be  entirely  removed,  and 
the  animal  will  live  for  months  afterward.     In  the 


THE  BRAIN. 


195 


human  being  it  is  so  plentifully  supplied  with  blood- 
vessels that,  if  its  removal  should  be  attempted,  the 
person  would  die  of  haemorrhage.  This  has  been 
the  invariable  result  of  experiments  on  the  higher 
kinds  of  animals,  as  the  dog  or  horse.  But  there  is 
no  doubt  that,  if  the  cerebrum  could  be  removed 
without  interfering  with  the  circulation  of  the  blood, 
even  a  human  being  would  continue  to  live  with- 
out it. 

246.  Structure  of  the  Cerebrum. — The  cerebrum 
(Fig.  58)  is  the  largest  part  of  the  brain,  forming  as 


Fig.  58. — Under  surface  of  the  brain,  showing  the  great  complexity  of  its 
structure.     At  the  lower  part  of  the  cut  is  the  cerebellum. 


196 


ORGANS  OF  CO-ORDINATION. 


it  docs  about  nine  tenths  of  the  whole  mass  within 
the  skull.  It  consists  of  two  halves,  called  hemi- 
spheres, the  dividing  fissure  running  from  the  front 
of  the  head  to  the  back ;  but  the  halves  are  not  en- 
tirely separated.  On  their  under  side,  a  bridge  or 
mass  of  white  fibers  runs  from  one  to  the  other,  and 
serves  as  a  means  of  nervous  communication  be- 
tween them.  The  cere- 
brum is  composed  of  both 
white  and  gray  matter,  the 
latter  being  spread  over 
the  surface,  and  the  former 
filling  up  the  interior,  and 
forming  the  greater  por- 
tion of  the  mass  (Fig.  59). 
The  arrangement  of 
the  nerve-matter  of  the 
cerebrum  is  very  peculiar. 


It  is  formed  into  folds  and 
wrinkles,  somewhat  like 
the  meat  of  an  English 
walnut.  These  folds  are 
called  the  convolutions  of 
the  brain,  and,  as  the  gray 
matter  follows  closely  the 
dipping  of  the  surface  be- 
tween the  convolutions,  it 
is  evident  that  the  amount 
of  gray  matter  is  much 
greater  than  it  would  be 
if  the  surface  of  the  brain 
were  smooth. 
It  has  been  found  by  experiment  that  the  nerve- 
matter    composing  the   cerebrum  is   insensible   to 


Fig.  59. — Section  of  thebrain,  show- 
ing the  arrangement  of  the  gray 
and  white  substance. 


THE  BRAIN. 


197 


ordinary  irritation.  Either  the  gray  or  the  white 
matter  may  be  cut,  pricked,  burned  with  fire  or 
caustic  acids,  without  producing  any  sensation. 
What,  then,  is  the  function  of  the  cerebrum  ? 

247.  Function  of  the  Cerebrum. — It  is  now  ac- 
knowledged by  all  who  have  paid  any  attention  to 
the  subject,  that  the  cerebrum  is  the  organ  of  thought. 
It  is  in  this  part  of  the  brain  that  all  ideas  have  their 
origin,  and  that  all  processes  of  reasoning  take  place. 
The  evidence  of  this  is  indirect,  but  very  conclusive, 
and  may  be  briefly  stated  as  follows : 

248.  Intelligence  increases  with  Increase  in  Size 
of  the  Cerebrum. — The  cerebrum  increases  in  size 
in  animals  as  we  pass  from  the  lower  forms  to  the 
higher.  The  superiority  of  one  animal  over  another 
in  the  scale  of  life  depends  mainly  upon  what  we 
call  intelligence.  Now,  we  find  that  the  intelligence 
of  animals  appears  to  increase  in  the  same  ratio  that 
the  size  of  the  cerebrum  increases  in  proportion  to 
the  rest  of  the  bodv.  In  the  fish,  the  cerebrum  is 
very  small,  and  his  intelligence  is  very  low.  In  the 
reptiles,  the  cerebrum  is  somewhat  larger,  and  their 
intelligence  as  a  class  greater.  In  birds,  the  relative 
size  of  the  cerebrum  is  considerably  increased,  and 
their  intelligence  is  proportionally  and  noticeably 
higher.  From  birds  we  pass  to  quadrupeds,  and 
here  is  a  great  increase  in  the  size  of  the  cerebrum, 
and  a  correspondingly  finer  intelligence.  As  we  go 
up  in  the  scale  of  quadrupeds,  we  find  the  size  of 
the  cerebrum  increasing  faster  than  the  size  of  the 
body  does,  until,  in  the  elephant,  we  find  a  brain 
weighing  eight  or  ten  pounds.  The  elephant  and 
the  whale  are  the  only  animals  whose  brains  are 
larger  than  man's,  and  even  their  immense  brains  are 


198  ORGANS  OF  CO-ORDINATION. 

much  smaller  relatively  to  the  size  of  their  bodies. 
The  human  brain  varies  in  weight  in  different  persons, 
but  its  average  weight  is  fifty  ounces,  or  about  three 
pounds.  These  facts,  then,  seem  to  show  a  relation- 
ship between  the  cerebrum  and  the  quality  of  intelli- 
gence, for  the  difference  in  weight  of  different  brains 
is  mainly  due  to  the  varying  size  of  the  cerebrum. 

249.  Size  of  Human  Brains. — When  we  examine 
different  brains  among  human  beings,  we  find  the 
same  general  law  holding  good.  Other  things  be- 
ing equal,  a  larger  brain  signifies  a  greater  mind. 
Thus  the  brain  of  Cuvier,*  the  celebrated  naturalist, 
weighed  64-J  ounces  ;  that  of  Abercrombie,f  physi- 
cian and  philosopher,  63  ounces,  and  that  of  Du- 
puytren,  \  surgeon,  62%  ounces  ;  while  the  brain  of 
an  idiot  seldom  exceeds  thirty  ounces  in  weight. 
Occasionally  men  have  possessed  great  intelligence, 
and  have  been  found  after  death  to  have  very  small 
brains.  An  example  of  this  is  the  brain  of  a  cele- 
brated mineralogist  (Haussmann),  who  is  said  to 
have  been  above  medium  stature.  Its  weight  was 
only  43.24  ounces.  In  such  cases,  it  is  usually  found 
that  the  convolutions  are  very  deep  and  very  much 
curved  and  turned  about,  so  that  there  is  a  greater 
amount  of  gray  matter  packed  away  than  would 
have  been  expected  in  so  small  a  skull. 

*  Baron  George  Chretien  Leopold  Frederic  Dagobert  Cuvier,  one 
of  the  most  eminent  of  modern  scientific  men  (i  769-1 832),  Professor 
of  Natural  History  in  the  College  of  France  ;  generally  considered  the 
founder  of  the  science  of  comparative  anatomy. 

f  John  Abercrombie,  a  distinguished  Scottish  physician  (1781-1844), 
especially  celebrated  for  his  metaphysical  writings. 

%  Baron  Guillaume  Dupuytren  (1777—1835),  during  his  lifetime  con- 
sidered the  most  eminent  surgeon  in  France  ;  Professor  of  Surgery  at 
Paris. 


THE  BRAIN. 


199 


250.  Effect  of  Injuries  of  the  Brain. — It  has  also 
been  noticed,  from  the  earliest  times,  that  injuries 
of  the  brain  produce  unconsciousness  and  various 
other  phenomena,  which  indicate  that  the  organ  of 
the  mind  has  been  injured  ;  so  that,  by  almost  all 
men,  the  fact  that  the  brain  is  the  seat  of  the  mind 
has  been  readily  acknowledged.  In  order  to  deter- 
mine what  particular  portion  of  the  brain  is  the 
organ  of  mental  processes,  experiments  have  been 
performed  on  animals.  As  has  previously  been 
mentioned,  the  cerebrum  can  not  be  removed  from 
the  higher  animals  without  causing  their  death  by 
haemorrhage,  but  in  birds  and  rabbits,  as  well  as  in 
the  reptiles,  it  can  be  done.  If  the  cerebrum  be  re- 
moved from  a  pigeon,  then,  what  is  the  effect  upon 
the  intelligence  ? 

251.  Removal  of  the  Cerebrum  of  a  Pigeon. — 
The   bird   passes   into   a   condition   of    stupor,   in 


Fig.  60. — Pigeon,  after  removal  of  the  cerebrum. 


which  he  takes  no  notice  of  anything  about  him 
(Fig.  60).     It  is  not  that  he  does  not  see  or  hear  or 


2oo  ORGANS  OF  CO-ORDINATION 

feel,  for  he  does  have  all  of  these  sensations.  If 
his  foot  be  pinched,  he  lifts  it  up,  and  then  puts  it 
down  again,  and  moves  uneasily,  showing  that  he 
feels  the  irritation.  His  eyes  will  follow  a  lighted 
candle,  which  is  moved  to  and  fro,  showing  that 
he  sees  it.  If  a  pistol  be  fired  behind  his  head,  he 
looks  around,  showing  that  he  heard  the  report, 
and  then  becomes  quiet  again,  relapsing  into  his 
condition  of  stupor.  What  do  these  facts  indicate  ? 
The  bird's  senses  are  perfect ;  he  sees,  and  hears, 
and  feels,  but  is  stupid.  All  the  impressions  upon 
his  senses  convey  no  idea  to  him,  or  rather  they 
give  rise  to  no  idea.  Noises  and  hurts,  which  in 
his  natural  state  would  frighten  him,  hardly  disturb 
him.  If  food  be  put  into  his  mouth,  he  swallows 
it,  but  he  will  make  no  attempt  to  feed  himself. 
In  fact,  every  action  and  every  response  to  irri- 
tation goes  to  show  that  he  has  lost  his  mind ;  his 
intelligence  is  gone  ;  he  no  longer  has  the  power  of 
reasoning  on  what  happens  to  him. 

252.  Disease  of  the  Human  Cerebrum. — And 
here,  as  in  the  case  of  the  spinal  cord,  we  find 
experiments  on  human  beings  provided  for  us  by 
Nature.  When  the  cerebrum  of  a  human  being  is 
diseased,  we  find  that  the  mind  is  affected.  This  is 
noticeably  the  case  in  the  disease  commonly  known 
as  softening  of  the  brain.  The  first  symptoms  in  this 
distressing  malady  are  mental  ones.  The  person 
begins  to  lose  his  memory ;  his  friends  probably 
perceive  it  before  he  does  himself ;  and  from  this 
first  indication  of  intellectual  feebleness  the  disease 
goes  on,  often  without  any  disturbance  of  the  nu- 
trition of  the  body,  until  the  intelligence  is  com- 
pletely abolished,  and  the  person's  life  is  a  blank. 


THE  BRAIN.  201 

When  the  brain  of  such  a  person  is  examined  after 
death,  the  cerebrum  is  the  part  found  diseased, 
and  we  see  that  the  gradual  impairment  and  ex- 
tinction of  the  mind,  which  we  have  watched  in  a 
human  being  as  the  result  of  disease,  is  really  the 
same  thing  as  the  sudden  destruction  of  the  mind 
which  we  produce  in  a  pigeon  by  a  surgical  opera- 
tion. 

253.  Recapitulation. — To  recapitulate;  the  evi- 
dence that  the  cerebrum  is  the  seat  of  the  intelligence  is 
the  following :  First,  we  see  that  in  the  lower  ani- 
mals, as  well  as  in  man,  the  development  of  the  mind 
is  proportionate  to  the  development  of  the  cerebrum 
in  comparison  with  the  rest  of  the  body.  Second, 
that  if  the  cerebrum  be  removed  from  an  animal, 
the  mental  faculties  are  the  only  ones  lost.  TJiird, 
when  the  mind  of  a  human  being  is  impaired  or 
lost,  we  find  a  corresponding  disease  or  injury  of 
the  cerebrum." 

254.  Structure  of  the  Cerebellum. — The  gan- 
glion next  in  size  to  the  cerebrum,  and  one  whose 
functions  are  of  great  importance,  is  the  cerebel- 
lum, or  little  brain  (Figs.  57,  58).  It  is  situated  be- 
neath the  back  part  of   the  cerebrum,  occupying 

*  Also,  when  the  cerebrum  is  seriously  injured,  the  mental  faculties 
are  generally  impaired.  There  have  been  some  cases  of  recovery  after 
very  severe  injuries  of  the  brain.  In  1850  a  young  man  in  Vermont,  a 
farm-hand,  was  blasting  rock,  when  a  tamping-iron,  three  and  a  half 
feet  long  and  an  inch  and  a  quarter  in  diameter,  was  driven  through 
his  head,  entering  the  left  cheek  and  coming  out  at  the  top  of  the  head, 
causing  a  great  loss  of  brain-substance.  He  recovered  completely  from 
the  wound,  but  from  a  quiet,  home-loving,  honest  lad,  he  developed 
into  a  tricky,  thieving  fellow,  of  a  roving  disposition,  lived  in  various 
places  in  South  America  and  the  United  States,  was  subject  to  epilep- 
tic fits,  and  died  in  convulsions  in  California  twelve  years  after  the  in- 
jury. 


202  ORGANS  OF  CO-ORDINATION. 

that  portion  of  the  skull  immediately  behind  the 
ears.  Its  average  weight  is  five  and  a  quarter 
ounces,  about  one  ninth  of  the  whole  weight  of 
the  brain.  It  is  composed  of  gray  and  white  mat- 
ter, arranged  in  much  the  same  way  as  in  the  cere- 
brum, excepting  that  the  convolutions  are  smaller 
and  dip  in  deeper,  so  that  in  the  cerebellum  the 
proportion  of  gray  matter  is  much  greater  than  in 
the  cerebrum.  This  fact,  of  itself,  would  indicate 
its  importance. 

255.  Function  of  the  Cerebellum. — The  exact 
function  of  this  part  of  the  brain  has  not  yet  been 
determined.  There  are  difficulties  in  the  way  of 
experiments  upon  it,  which  are  not  found  in  experi- 
ments upon  the  cerebrum.  If  the  entire  cerebellum 
be  removed  from  a  pigeon,  the  bird  dies  from 
haemorrhage,  and  nothing  can  be  learned.  If  the 
greater  part  of  it  be  removed,  proper  precautions 
being  taken  against  haemorrhage,  very  peculiar 
phenomena  are  presented.  The  pigeon  sprawls 
about  in  frantic  efforts  to  get  away,  but  acts  like  a 
drunken  man  (Fig.  61).  He  does  not  seem  to  pos- 
sess proper  control  over  his  muscles.  The  muscles 
act  perfectly  well ;  there  is  no  paralysis,  but  the 
harmonious  action  of  sets  of  muscles  is  apparently 
interfered  with.  To  move  the  wings  for  flying,  or 
the  legs  in  walking,  requires  the  consentaneous 
action  of  many  muscles,  and  this  the  bird  is  unable 
to  control. 

This  experiment,  which  invariably  produces  the 
same  results,  seems  to  show  that  the  cerebellum  in 
some  way  controls  and  harmonizes  the  voluntary 
muscular  contractions,  or,  as  the  physiologists  ex- 
press it,  the  cerebellum  is  the  seat  of  the  co-ordi- 


THE  BRAIN. 


203 


nating   power  in  voluntary  muscular  movements. 
This   idea  was   at   one   time   accepted,  but  it  was 


Fig.  61. — Pigeon,  after  removal  of  the  cerebellum. 


found  that  in  pigeons,  who  did  not  die  from  the 
operation,  the  power  of  co-ordinating  their  move- 
ments was  after  a  time  regained.  And  this  was  not 
the  result  of  the  healing  of  the  injury,  for  the  lost 
portion  of  the  cerebellum  is  found  on  inspection  not 
to  have  been  renewed. 

Diseases  of  this  portion  of  the  brain  in  the  hu- 
man being  also  give  contradictory  data.  Tumors 
and  injuries  of  the  cerebellum  often  occasion  diffi- 
culty in  muscular  co-ordination,  but,  on  the  other 
hand,  no  disturbance  in  the  muscular  movements 
has  been  detected  in  some  cases,  where  the  disease 
of  the  cerebellum  has  been  very  extensive. 

Comparison  of  the  relative  development  of  the 
cerebellum  in  different  animals  seems  to  favor  the 
theory  proposed. 

All  things  considered,  however,  scientific  men 


204 


ORGANS  OF  CO-ORDINATION. 


are  agreed  that  the  real  function  of  the  cerebellum  is 
not  yet  definitely  known. 

256.  Other  Ganglia  of  the  Brain. — Besides  the 
cerebrum  and  cerebellum,  there  are  various  ganglia 
of  less  size,  all  of  which  are  situated  on  or  near  the 
under  surface  of  the  brain.  Experiments  upon  these 
are  very  difficult,  and  have  been  hitherto  unproduc- 
tive of  results.  It  is  an  undoubted  fact,  however, 
that,  unless  destroyed  by  loss  of  blood,  an  animal 
will  continue  to  live  after  the  cerebrum  and  cerebel- 
lum have  been  removed,  showing  that  these  latter 
organs  are  not  essential  to  life.  Of  the  remaining 
ganglia,  the  tuber' cula  quadrigem' ina  *  are  known  to 
be  the  centers  by  which  vision  is  rendered  possible. 
The  optic  nerves  take  their  origin  in  these  small 
ganglia,  and  the  fact  that  they  receive  the  impres- 
sions which  we  call  sight  is  proved  in  this  way :  If 
the  optic  nerve  be  cut  between  the  eye  and  the  tu- 
bercula  quadrigemina,  blindness  results.  The  same 
effect  is  produced  by  destruction  of  these  bodies, 
the  optic  nerves  remaining  uninjured.  If,  on  the 
other  hand,  the  connections  between  these  ganglia 
and  the  cerebrum  be  severed,  the  ganglia  and  nerves 
remaining  intact,  sight  still  remains,  and  vision  is 
also  retained,  if  the  cerebrum  be  removed  and  the  tu- 
bercula  quadrigemina  left  untouched.  These  things 
are  sufficient  to  show  that  they  are  the  centers  of 
the  sense  of  vision. 

In  some  one  or  all  of  the  remaining  ganglia, 
with  the  exception  of  the  medulla  oblongata,  to  be 
hereafter  described,  the   powers  of   sensation  and 

*  These  small  bodies  are  situated  above  and  in  front  of  the  cere- 
bellum, between  it  and  the  cerebrum,  and  so  are  not  shown  in  any  of 
the  cuts. 


THE  BRAIN.  205 

motion  reside.  This  is  known  from  the  fact  that, 
after  the  removal  of  the  cerebrum  and  cerebellum, 
the  animal  is  still  capable  of  sensation  and  voluntary 
motion ;  but,  if  all  the  ganglia  be  removed,  except- 
ing the  medulla,  not  only  does  consciousness  dis- 
appear, but  all  sensation  and  voluntary  movements 
cease,  the  special  senses  are  abolished,  and  the  only 
manifestations  of  life  are  the  continuance  of  the 
functions  of  respiration  and  circulation,  and  the  re- 
flex movements  of  the  parts  connected  with  the 
spinal  cord. 

257.  The  Medulla  Oblongata. — The  spinal  cord 
passes  upward  from  the  spinal  canal  into  the  skull. 
Just  after  entering  the  cavity  of  the  skull,  it  be- 
comes somewhat  enlarged,  and  this  enlarged  por- 
tion is  called  the  medulla  oblongata  (Figs.  57,  58). 
It  is  about  an  inch  and  a  quarter  long,  and  three 
quarters  of  an  inch  wide,  and  at  its  upper  extremity 
is  merged  in  other  parts  of  the  brain.  Imbedded 
in  this  part  of  the  cord  is  a  small  mass  of  gray  mat- 
ter, which  is  more  essential  for  the  actual  preserva- 
tion of  life  than  any  other  portion  of  the  brain.  It 
has  sometimes  been  called  the  "  vital  knot."  If  this 
be  destroyed,  all  manifestations  of  life  instantly 
cease.  The  cause  of  this  is  the  intimate  relation 
which  this  part  bears  to  the  function  of  respiration. 

258.  The  Medulla  Oblongata  controls  Respira- 
tion.— The  movements  of  respiration  are  to  a  cer- 
tain extent  under  the  control  of  the  will,  but,  under 
ordinary  circumstances,  we  breathe  unconsciously. 
Inspiration  and  expiration  take  place  regularly  and 
unceasingly,  by  night  and  by  day,  in  our  sleeping 
as  well  as  our  waking  hours.     The  nervous  supply, 

therefore,  by  which  this  function  is  controlled  is, 
10 


206  ORGANS  OF  CO-ORDINATION. 

so  to  speak,  automatic.  The  requisite  movements 
are  carried  on  by  reflex  action.  How  is  this  accom- 
plished ? 

As  the  processes  of  repair  and  waste  go  on,  car- 
bon dioxide  and  other  waste  matters  accumulate  in 
the  blood.  When  this  venous  blood,  loaded  with 
impurities,  arrives  at  the  lungs,  it  imparts  a  peculiar 
stimulus  to  the  large  nerves,  which  are  distributed 
to  these  organs.  They  convey  a  sensation  to  the 
medulla  oblongata,  and  the  corresponding  motor 
nerves  convey  the  impulse  from  the  gray  matter  of 
the  medulla  oblongata,  and  cause  a  contraction  of 
the  muscular  walls  of  the  chest.  Inspiration  then 
takes  place,  the  blood  receives  oxygen,  the  air  is 
expired  again,  and  the  chest-walls  remain  passive 
until  venous  blood  again  accumulates  in  the  lungs 
in  sufficient  quantity  to  cause  the  requisite  stimulus 
in  the  medulla  oblongata ;  and  so  the  process  con- 
tinues through  a  long  life,  independently  of  the  will 
of  the  individual. 

259.  Automatic  Action  of  the  Medulla  Oblongata. 
— Respiration,  however,  is  in  a  measure  under  the 
control  of  our  will.  We  can  hold  our  breath,  if  we 
choose,  for  a  short  time ;  but,  with  the  cessation  of 
respiration,  the  blood  becomes  more  and  more 
charged  with  impurities,  until  at  length  a  peculiar 
sensation  begins  to  be  felt,  which  we  call  "  want  of 
breath/'  or  "  shortness  of  breath."  If  we  still  resist 
the  desire  to  inspire,  and  hold  the  chest-walls  im- 
movable, this  sensation  increases  until  it  induces  the 
most  intense  suffering,  and  the  will  is  at  length  un- 
able to  assert  its  power.  The  automatic  action  of 
the  medulla  oblongata  overrides  our  feeble  opposi- 
tion, and  we  breathe  again,  in  spite  of  ourselves.     It 


THE  BRAIN. 


207 


is  a  lesser  degree  of  this  same  sensation,  without  a 
doubt,  which  acts  as  a  constant  stimulus  to  the  me- 
dulla oblongata,  and  keeps  up  the  process  of  respi- 
ration without  our  consciousness.  Now,  when  the 
portion  of  the  medulla  oblongata  containing  this 
part,  called  "  the  vital  knot,"  is  destroyed,  res- 
piration instantly  ceases,  and  the  circulation  soon 
stops.  This  is  the  quickest  way  known  of  killing 
animals,  and  is  much  used  by  physiologists,  when 
they  wish  to  produce  sudden  death,  without  injur- 
ing the  blood-vessels  or  other  organs  of  the  body 
on  which  they  wish  to  experiment.* 

*  In  the  great  slaughtering  establishments  of  the  West,  cattle  are 
killed  by  puncture  of  the  medulla  oblongata.  Men  stand  upon  a  raised 
platform,  and,  as  the  animals  pass  underneath,  penetrate  this  organ 
with  a  sharp  spear,  or  with  a  bullet  from  a  carbine.  The  matador^  in 
the  Spanish  bull-fights,  also  aims  to  strike  this  vital  part,  and  his  repu- 
tation depends  upon  the  success  with  which  he  does  it.  The  Spaniards 
execute  criminals  upon  the  same  plan,  by  means  of  the  garotte,  which 
consists  of  an  iron  collar  surrounding  the  throat,  with  a  steel  pin  pro- 
jecting inward  behind.  A  single  turn  of  a  large  wheel  forces  this  pin 
into  the  medulla  oblongata  and  causes  instant  death. 


CHAPTER  V. 


SPECIAL  NERVES. — HYGIENE. 


260.  Nerves   of  the    Head   and    Face. — In   the 

spinal  nerves,  we  have  seen  that  the  motor  and 
sensory  fibers  are  mingled,  so  that  each  nerve  con- 
tains fibers  of  both  kinds.  In  the  nerves  coming 
from  the  brain  this  is  commonly  not  the  case.     As 

a  rule,  some  nerves  are 
entirely  nerves  of  sensa- 
tion, and  others  entirely 
nerves  of  motion,  and 
the  two  functions  are 
not  united  in  a  single 
trunk.  These  nerves 
are  arranged  in  pairs, 
like  the  spinal  nerves, 
one  going  to  one  side 
of  the  head  or  face  and 
the  other  to  the  other. 

The  two  most  im- 
portant nerves  of  the 
face  are  those  called 
the  trigeminal  and  the 
facial.  The  trigeminal 
nerve  (Fig.  62)  emerges  from  the  skull  by  three 
openings,  being   divided  into  three   branches  just 


Fig.  62. — Diagram  showing  the  distri- 
bution of  the  fifth  nerve  to  the  face. 


SPECIAL  NERVES.— HYGIENE. 


209 


before  it  reaches  these  openings.  One  branch  sup- 
plies the  parts  surrounding  the  eye,  the  forehead, 
and  the  inside  of  the  nose ;  the  second  comes  out 
just  below  the  eye,  after  sending  branches  to  the 
teeth  of  the  upper  jaw,  and  supplies  the  cheek, 
the  upper  lip,  and  the  outside  of  the  nose ;  while 
the  third  comes  out  at  a  point  near  the  front  of  the 
lower  jaw,  and  supplies  the  chin  and  lower  lip,  be- 
sides having  sent  branches  to  the  teeth  and  tongue, 
before  emerging  from 
the  jawbone.  These 
nerves  are  the  great 
nerves  of  sensation  of 
the  face,  and  are  gener- 
ally considered  to  be 
the  most  exquisitely 
sensitive  nerves  in  the 
whole  body.  They  are 
often  the  seat  of  neu- 
ralgia, and  give  rise  to 
the  most  intense  and 
intolerable  suffering. 

The  facial  nerve 
(Fig.  63)  is  the  motor 
nerve  of  the  face ;  it 
emerges  from  the  skull 

just  below  the  ear,  and,  passing  forward  through 
the  parotid  gland,  is  distributed  to  all  the  muscles 
of  the  face.  Paralysis  of  this  nerve  is  far  from  un- 
common, and  produces  a  most  singular  and  charac- 
teristic effect  upon  the  countenance.  Exactly  one 
half  of  the  face  loses  all  expression,  as  much  as  if 
dead,  and  the  contraction  of  the  muscles  of  the  op- 
posite side,  not  being  in  any  way  counteracted,  pro- 


FlG.  63. — Diagram  showing  the  distri- 
bution of  the  facial  nerve  to  the  face. 


2io  ORGANS  OF  CO-ORDINATION. 

duces  dreadful,  though  often  ludicrous,  distortion 
of  the  features.  This  form  of  paralysis  often  occurs 
among  hackmen  and  others  who  are  exposed  to 
stormy  weather.  If  a  strong  wind,  particularly 
when  accompanied  by  snow  or  sleet,  be  allowed  to 
beat  upon  the  side  of  the  face,  there  is  great  danger 
of  paralysis  of  the  facial  nerve.  Such  exposure  of 
the  place  where  this  nerve  emerges  from  the  skull 
should  be  carefully  avoided. 

261.  The  Sciatic  Nerve. — Each  limb  of  the  body 
is  supplied  by  large  nerve-trunks,  which,  as  a  rule, 
follow  very  nearly  the  course  of  the  arteries.  The 
largest  nerve  of  the  leg,  however,  runs  down  be- 
hind the  limb,  while  the  femoral  artery  runs  down 
the  front  of  the  thigh.  This  nerve  is  known  as 
the  sciat'ic,  and  its  branches  extend  to  the  foot. 
It  is  this  nerve  which,  when  pressed  upon  in  sitting, 
gives  rise  to  the  sensation  commonly  described  as 
the  "  foot  being  asleep." 

262.  Importance  of  Reflex  Action. — It  is  impor- 
tant to  call  attention  to  the  fact  that  reflex  action  has 
a  great  deal  to  do  with  our  health  and  safety,  even 
when  the  spinal  cord  and  brain  are  in  perfect  con- 
dition. People  in  general  are  hardly  aware  how 
much  they  owe  to  this  property  of  the  nervous  sys- 
tem in  time  of  danger.  Familiar  illustrations  are 
found  in  the  rapid  recovery  of  the  bodily  equilib- 
rium, when  the  foot  has  slipped  ;  in  the  involun- 
tary start  and  assumption  of  a  position  of  defense, 
when  a  horse  and  wagon  suddenly  run  upon  one  in 
the  street ;  in  the  start  of  the  body  at  a  sudden 
noise  ;  in  the  instantaneous  withdrawal  of  a  portion 
of  the  body  Avhen  it  is  burned  ;  in  the  winking  of 
the  eyelids,  particularly  at  indications  of   danger  ; 


SPECIAL  NERVES.— HYGIENE.  2II 

and  in  hundreds  of  daily  actions,  which  follow  so 
instantaneously  upon  the  application  of  a  stimulus, 
that  the  thought,  or  mental  appreciation  of  the 
stimulus,  does  not  come  until  after  the  reflex  action 
has  already  taken  place.* 

When  we  consider  the  immense  number  of  such 
actions  which  take  place  every  hour  of  the  day.  and 
the  stupendous  work  of  nutrition,  with  its  compli- 
cated phenomena,  all  going  on  outside  of  our  con- 
trol, we  see  that  in  all  probability  the  greater  part 
of  the  nervous  force  expended  in  the  body  goes  to 
produce  involuntary  movements,  and  to  control  and 
preserve  the  health  and  integrity  of  our  organism 
in  spite  of  ourselves.  It  is  a  suggestive  thought 
that,  much  as  we  appear  to  be  our  own  masters, 
independent  as  we  seem  to  be  of  the  outside  world, 
we  are  really  ruled  by  the  general  vital  forces 
which  equally  rule  all  animals  and  even  plants, 
upon  which  we  are  all  equally  dependent,  and  over 
which  what  we  call  "  we  "  have  almost  as  little  con- 
trol in  ourselves  as  in  the  lion  that  roams  the  des- 
ert or  in  the  grass  that  grows  beneath  our  feet. 

263.  Education  of  the  Nervous  System. — The 
hygiene  of  the  nervous  system  has  to  do  mainly  with 
the  problem  of  education,  and  with  the  over-  or  un- 
der-use  of  its  parts.  Education  is  a  broad  subject, 
and  can  not  be  taken  up  here,  but  it  is  undoubtedly 

*  It  is  related  of  a  distinguished  chemist  that  a  glass  vessel  once 
exploded  in  his  hands  and  was  blown  into  a  thousand  pieces.  His 
hands  were  severely  lacerated,  and  he  at  first  feared  that  his  sight  was 
destroyed  ;  but  on  examination  it  was  found  that  he  had  closed  his  eye- 
lids involuntarily  at  the  instant  of  the  explosion,  and,  although  the  lids 
had  been  wounded  in  many  places  by  the  flying  bits  of  glass,  the  eyes 
were  uninjured.  The  rapidity  of  such  reflex  action  far  surpasses  that 
of  any  voluntary  movement. 


212  ORGANS  OF  CO-ORDINATION. 

true  that  in  the  future  much  more  attention  will  be 
paid  than  in  the  past  to  the  physical  conditions 
which  underlie  all  development  and  training  of  the 
mental  powers.  It  is  known  that  repetition  of  the 
same  process  in  any  portion  of  the  nervous  system 
renders  it  every  time  more  and  more  easy.  The 
result  of  such  repetition  is  what  we  call  habit.  The 
more  impressible  and  easily  stimulated  the  different 
parts  of  the  nervous  system  are,  therefore,  the  more 
readily  habits  will  be  formed  and  the  more  firmly 
they  will  become  fixed.  Now,  the  cells  and  fibers 
of  the  nervous  S}rstem  of  young-  and  growing  ani- 
mals, like  those  of  their  muscular  system,  are  espe- 
cially soft  and  yielding,  and,  as  they  are  constantly 
growing,  the  changes  in  them  are  more  frequent, 
and  they  are  much  more  easily  influenced  by  any 
stimulus  than  those  of  adults.  Consequently  chil- 
dren and  youths  are  especially  liable  to  form  habits, 
and,  in  order  to  prevent  the  formation  of  bad  ones, 
they  need  the  guidance  and  protection  of  older  per- 
sons. The  experience  of  the  young  is  not  wide 
enough  to  inform  them  correctly  of  what  is  good 
and  what  is  bad,  nor  is  it,  in  most  cases,  sufficient 
to  enable  them  to  appreciate  the  wisdom  of  the 
advice  or  commands  of  older  persons.  For  these 
reasons  it  is  necessary,  in  the  training  of  the  young, 
to  require  what  often  seems  to  them  unreasonable, 
and  to  forbid  things  with  what  may  seem  to  them 
foolish  pertinacity.  It  is  "this  readiness  with  which 
habits  are  formed  in  the  young,  and  the  firmness 
with  which  they  become  fixed,  that  render  it  so 
dangerous  for  them  to  indulge  in  sensual  gratifica- 
tions, such  as  the  drinking  of  liquids  containing 
alcohol,  or  to  join  in  games  which  excite  the  selfish 


SPECIAL  NERVES.— HYGIENE. 


213 


emotions  in  a  high  degree,  such  as  lotteries  and 
gambling. 

It  is  this  ease  of  habit-forming  in  the  young,  too, 
that  renders  childhood  and  youth  the  desirable  time 
for  both  mental  and  physical  training.  In  fact,  the 
nervous  system  is,  at  this  time,  so  impressionable  that 
the  training  will  take  place  inevitably,  whether  it  is 
directed  or  not,  and  the  success  or  failure  of  adult 
life  is  generally  determined  by  the  conditions  under 
which  the  years  below  twenty  have  been  passed. 

264.  Importance  of  exercising  the  Brain. — The 
nervous  system,  like  the  muscular,  must  be  suffi- 
ciently exercised,  in  order  to  remain  vigorous  and 
healthy.  If  the  brain  be  allowed  to  remain  indo- 
lent, the  faculties  of  memory  and  attention,  the 
power  of  concentrating  the  thoughts,  will  be  con- 
siderably weakened.  It  will  be  found  that  even 
the  inactivity  of  a  few  weeks'  vacation  will  render 
it  a  matter  of  some  difficulty  at  first  to  keep  the 
brain  at  work  at  one's  ordinary  duties.  Judicious 
exercise  also  will  strengthen  special  mental  facul- 
ties, just  as  proper  training  will  develop  muscular 
power.  The  retentiveness  of  the  memory  may  be 
immensely  increased,  and  the  facility  with  which 
the  daily  mental  labor  of  the  professional  man  is 
performed,  together  with  the  increased  efficiency 
as  age  advances,  shows  the  effect  of  directing  the 
nutritive  processes  constantly  in  the  same  direction. 
In  fact,  this  tendency  is  so  strong  that  specialists, 
all  of  whose  energies  for  many  years  are  directed 
upon  a  particular  subject,  are  very  apt  to  become 
narrow-minded  or  "  lop-sided,"  and  unable  to  see 
more  than  one  side  of  any  subject,  and  that  some- 
times the  least  important  one. 


2 1 4  ORGANS  OF  CO-ORDINA  TION. 

265.  Danger  of  Over-Exercise. — On  the  other 
hand,  too  much  exercise  is  as  injurious  as  too  little. 

.  All  brain-work,  as  well  as  muscular  work,  involves 
a  waste  of  tissue.  As  we  are  thinking,  our  brains 
are  wearing  out.  And  while  this  organ  is  actively 
employed,  the  waste  of  tissue  is  greater  than  the 
repair.  When  this  excess  of  waste  has  reached  such 
a  point  that  the  proper  working  of  the  brain  is  inter- 
fered with,  we  begin  to  feel  incapable  of  further 
study,  the  attention  begins  to  waver,  problems  seem 
difficult  that  at  other  times  would  be  easy,  and 
perhaps  the  memory  is  at  fault.  Such  a  condition 
demands  imperative  rest,  and  this  rest  is  obtained 
by  sleep. 

266.  Sleep. — During  sleep,  the  repair  of  all  the 
tissues  goes  on  with  great  rapidity.  As  the  body  is 
inactive,  even  the  brain  being  in  sound  sleep  en- 
tirely unoccupied  with  thought,  the  waste  of  the 
tissues  is  very  small,  almost  the  whole  of  it  being 
the  result  of  the  organic  processes  of  circulation, 
respiration,  and  digestion.  In  all  of  these  organic 
processes,  which  must  be  practically  continuous, 
rest  is  obtained  at  short  intervals,  the  activity  of 
the  organs  concerned  in  them  being  intermittent, 
and,  although  the  intervals  of  rest  are  very  short, 
they  are  so  numerous  that  they  make  up  together 
about  half  of  the  twenty-four  hours.  But  the  mus- 
cular and  nervous  systems  have  no  such  frequent 
intervals  of  rest  during  waking  hours,  the  brain,  in 
particular,  being  constantly  active,  so  that  their  rest 
has  to  be  taken  continuously  in  the  form  of  sleep. 

During  sleep,  therefore,  the  repair  of  tissue  runs 
vastly  ahead  of  the  waste,  and  the  exhausted  parts 
have  their  vigor  and  irritability  rapidly  restored. 


SPECIAL  NERVES.— HYGIENE. 


215 


As  the  special  senses  and  the  sensitiveness  of  the 
muscular  and  nervous  systems  had  become  dulled 
and  torpid  because  they  were  wasting  away,  so  now, 
as  they  are  built  up  again,  their  sensitiveness  re- 
turns, and  slight  stimuli  are  sufficient  to  arouse  them 
into  activity.  We  then  wake  up.  Even  the  morn- 
ing  light  may  produce  a  sufficient  effect  upon  the 
eye,  through  the  closed  lids,  to  waken  the  sleeper, 
and  he  rises  refreshed  for  the  work  of  another  day. 
The  best  time  for  sleep  is  night,  because  it  is 
dark  and  quiet ;  the  natural  stimuli  of  the  eyes  and 
ears  are  absent,  and  therefore  rest  can  be  obtained 
with  the  least  likelihood  of  being  broken.  It  is  a 
good  rule  for  all  persons  to  go  to  bed  before  mid- 
night, and  rise  within  ten  minutes  after  waking  in 
the  morning.  The  amount  of  sleep  required  by 
each  individual  must  be  determined  by  himself 
from  experience.  For  most  persons  eight  hours  is 
not  too  much,  and  many  can  do  with  less.*     Chil- 

*  Marvelous  stories  are  told  of  persons  who  can  get  along  with  very 
little  sleep.  In  most  cases,  if  sleep  is  dispensed  with  at  one  time,  it 
must  be  made  up  at  another,  and  some  people  possess  the  faculty  of 
falling  asleep  at  odd  moments,  and  making  up,  by  what  are  sometimes 
called  "  cat-naps,"  for  the  loss  of  regular  sleep.  Thus,  Napoleon  Bona- 
parte is  said  to  have  been  satisfied  with  four  hours'  sleep  in  the  twenty- 
four  ;  but  this  only  refers  to  the  time  he  spent  in  bed.  He  was  in  the 
habit  of  sleeping  on  horseback  during  a  march,  and  his  traveling-coach 
was  made  expressly  so  that  the  interior  could  be  arranged  as  a  bed.  He 
often  fell  asleep,  too,  for  a  few  minutes  at  a  time,  in  his  study,  with  his 
head  resting  on  his  arms  on  a  desk  in  front  of  him.  It  maybe  doubted 
whether  any  person  could  live  long  with  only  four  hours'  sleep  a  day. 

The  Chinese  sometimes  punish  criminals  by  confinement  in  a  cage 
where  they  can  neither  stand  up  nor  sit  or  lie  down.  Attendants  are 
stationed  to  prevent  the  miserable  men  from  falling  asleep  ;  for  even 
under  such  conditions  exhaustion  brings  on  sleep.  The  unfortunate 
men  are  pricked  and  pinched,  and  by  various  means  of  torture  kept 
awake  until,  as  a  rule,  in  eight  or  ten  days,  they  die  raving  maniacs. 


2i6  ORGANS  OF  CO-ORDINATION. 

dren  need  more,  in  proportion  to  their  fewness  of 
years,  and  old  people  sometimes  need  less,  because 
of  their  comparative  inactivity  during  their  waking 
hours. 

267.  Abuse  of  the  Nervous  System. — A  word  of 
caution  should  be  spoken  about  the  various  forms 
of  indulgence  which  affect  the  sympathetic  system 
of  nerves.  These  include  all  those  forms  of  sensual 
gratification  which  are  accompanied  by  a  high  de- 
gree of  physical  pleasure,  followed  by  a  more  or 
less  protracted  period  of  depression.  This  depres- 
sion, an  instance  of  which  is  seen  in  the  reaction 
following  intoxication,  is  the  result  of  a  great  shock 
and  consequent  great  waste  of  tissue  in  the  sympa- 
thetic nervous  system.  Recovery  from  such  shocks 
is  very  slow.  The  sympathetic  ganglia  have  to  do 
with  the  important  function  of  nutrition.  They  lie 
at  the  very  foundation  of  life  in  our  bodies.  Their 
ordinary  duties  are  severe,  and  about  all  they  can 
attend  to  properly.  Therefore,  any  great  shock  to 
this  part  of  the  nervous  system  affects  the  very  cen- 
ters of  life.  This  is  the  reason  of  the  "  breaking 
up,"  as  it  is  called,  which  results  from  the  various 
forms  of  dissipation.  This  word  "  dissipation  "  is 
well  used  for  such  acts  as  are  commonly  included 
under  this  head,  as  all  kinds  of  debauchery,  abuse 
of  the  digestive  organs,  late  hours,  insufficient  sleep 
and  relaxation,  etc.,  dissipate  nervous  force  with 
frightful  rapidity. 


PART    V. 
ORGANS   OF  PROTECTION. 


CHAPTER  I. 

THE   SKIN. 

268.  The  Skin. — The  skin,  with  its  appendages, 
is  a  complex  organ,  and  has  many  functions.  It 
serves  for  protection,  contains  nerves  of  sensation, 
secretes,  absorbs,  and  excretes,  and  its  functions  are 
so  necessary  to  life  that,  if  in  any  way  it  be  rendered 
unable  to  perform  its  duty  in  the  organism,  death  is 
the  result. 

269.  Structure  of  the  Skin. — The  skin  is  com- 
posed essentially  of  two  layers,  one  called  the  cuticle 
or  epidermis,  and  the  other  the  cutis  or  derma  (Fig. 
63).*  The  former  is  the  outside  layer,  and  the  lat- 
ter the  inside.  The  epidermis  consists  of  small,  flat- 
tened, dry  scales,  and  receives  the  brunt  of  injuries 
and  abrasions.  The  thickness  of  this  layer  is  shown 
in  a  blister,  the  epidermis  being  there  separated 
from  the  layer  beneath  by  the  fluid  which  fills  the 
vesicle. f      The   inner   layer,  or  derma,  constitutes 

*  Cutis  is  the  Latin  for  skin,  and  cuticle  means  little  skin ;  derma 
is  the  Greek  for  skin,  and  epidermis  means  the  outer  layer  of  the  skin, 
or.  literally,  "  upon  the  skin." 

f  Vesicle  is  from  the  Latin,  and  means  a  bladder,  which  a  blister 
somewhat  resembles. 


218 


ORGANS  OF  PROTECTION. 


what  is  sometimes  called  the  true  skin.     This  layer 
alone  contains  nerves,  blood-vessels,  hair-bulbs,  and 


Hnir. 


^^''^^S^^'s^'' '    \ 


Epidermis. 

Pigment-cells. 
Papillae. 


Derma. 


Sweat-glands. 


Fatty  tissue. 


Fig.  64. — Diagram  representing  a  vertical  section  of  the  skin.     Attached  to 
the  hair  are  two  sebaceous  glands. 


the  other  appendages  of  the  skin.  It  is  made  up  of 
strong  interlacing  fibers  of  connective  tissue,  which 
form  a  firm,  close  covering  for  the  delicate  tissues 
beneath.  This  layer  varies  in  thickness  in  different 
parts  of  the  body,  from  one  fiftieth  to  about  one  sixth 
of  an  inch.  For  instance,  the  skin  of  the  eyelid  is 
very  thin,  while  that  of  the  small  of  the  back  is  the 
thickest  in  the  body. 

270.  The  Derma.  —  The  under  surface  of  the 
derma  is  merged  in  the  loose  connective  tissue 
which  lies  between  the  skin  and  the  flesh.  It  is  in 
this  loose  tissue  that  fat  accumulates,  and,  in  conse- 
quence of  its  peculiarly  loose  and  flexible  structure, 
the  skin  can  be  moved  easily  in  any  direction,  slip- 
ping or  gliding,  with  no  pain  and  no  disagreeable 
sensation,  over  the  tissues  immediately  beneath  it. 
The  upper  surface  of  the  derma  is  covered  with 


THE  SKIN.  2lg 

little  elevations,  called  papil'lce,  which,  on  an  aver- 
age, are  about  -j-J-g-  of  an  inch  in  length,  and  -^^  of 
an  inch  broad  at  the  bottom.  They  are  somewhat 
conical  in  shape,  and  in  their  interior  are  found  the 
ends  of  sensitive  nerves.  In  some  parts  of  the 
body  they  are  scattered  irregularly  on  the  surface 
of  the  derma,  while  in  other  regions  they  are  ar- 
ranged in  rows,  and  produce  the  appearance  of 
small  parallel  ridges  on  the  surface  of  the  body. 
This  latter  arrangement  is  most  distinctly  to  be 
seen  on  the  palm  of  the  hand  and  fingers,  and  in 
these  parts  also  the  sense  of  touch  is  most  highly 
developed. 

271.  The  Epidermis. — The  epidermis  lies  in  im- 
mediate contact  with  the  derma,  its  under  surface 
being  accurately  molded  to  fit  the  papillae.  But,  in 
the  under  portion  of  it,  the  portion  into  which  the 
papillae  project,  the  scales,  instead  of  being  flat  and 
hard,  are  rounded  and  soft,  and  contain  a  certain 
amount  of  coloring -matter,  in  the  form  of  small, 
dark  granules.  As  this  part  of  the  epidermis 
varies  in  color  and  thickness,  so  the  complexion 
of  the  person  varies.*  In  the  negro,  these  pig- 
ment-cells, as  they  are  called,  are  very  dark  and 
numerous,  and  there  are  all  gradations  in  the 
amount  of  the  coloring-matter  in  different  persons, 
from  the  coal-black  African  to  the  albino,  in  whom 
there  is  no  color  at  all,  except  the  red  tinge  given 
by  the  blood. 

*  This  layer  of  pigment-cells  seems  to  protect  the  parts  beneath 
from  the  action  of  the  sun.  The  natives  of  all  tropical  countries  are 
dark,  and  exposure  to  the  sun's  rays,  even  in  our  climate,  tans  the  skin 
to  a  darker  hue.  Sometimes  this  effect  of  the  sun  is  more  noticeable 
in  particular  spots,  producing  what  are  known  as  freckles. 


220  ORGANS  OF  PROTECTION, 

272.  The  Nails. — Near  the  ends  of  the  fingers 
and  toes  the  skin  takes  on  a  peculiar  appearance. 
The  epidermis  is  very  closely  applied  to  the  derma, 
with  no  colored  cells  between  them,  and  the  scales 
of  which  it  is  composed  are  singularly  dry  and 
hard,  and  semi-transparent.  These  peculiar  growths 
are  called  the  nails.  The  part  of  the  finger  from 
which  they  grow  is  called  the  root  of  the  nail,  and 
the  nail  grows  both  in  length  and  thickness.  It  is 
formed  by  the  continual  pushing  forward  of  new 
cells,  both  from  the  root  and  from  the  under  sur- 
face. The  growth  from  the  root  makes  it  grow  in 
length,  while  the  addition  of  cells  on  the  under 
surface  renders  it  thicker  at  the  forward  end  than 
it  is  near  the  root.  The  nails  were  probably  once 
a  means  of  defense  and  offense,  when  men  were  in  a 
low,  barbarian  state ;  but,  at  the  present  day,  their 
chief  value  appears  to  be  for  ornament,  and  as  a 
support  for  the  pulp  of  the  finger.* 

273.  The  Hair. — The  hairs  are  peculiar  growths 
of  the  skin.  At  certain  points  the  surface  of  the 
skin  seems  to  dip  inward,  forming  a  deep  pit  or 
pocket,  at  the  bottom  of  which  is  a  little  projection 
or  papilla.  From  this  papilla  the  hair  grows,  and, 
emerging  from  the  pocket,  attains  in  some  parts  of 
the  body  a  considerable  length.-)*  The  body,  or 
shaft,  of  a  hair  consists  of  cells,  flattened  and  hard, 
but  through  its  center,  from  one  end  to  the  other, 

*  The  nails  are  of  special  use  in  the  way  last  mentioned.  The 
finger-tips  are  extremely  sensitive,  and  the  hard,  stiff  nail  serves  as  a 
backing  against  which  it  can  be  pressed  by  the  objects  it  touches.  In 
this  way  the  nails  increase  materially  the  delicacy  of  touch. 

\  Instances  have  been  known  of  women  with  hair  six  or  seven  feet 
in  length,  and  of  men  whose  beards  measured  nearly  as  much.  Such 
cases,  however,  are  very  rare. 


THE  SKIN.  221 

runs  a  hollow  canal,  filled  with  pigment-cells.  These 
cells,  according  to  the  amount  of  the  coloring-mat- 
ter in  them,  give  the  hair  the  appearance  known  as 
black,  brown,  gray,  auburn,  etc.  Almost  the  whole 
surface  of  the  body  is  covered  with  hair,  excepting 
the  palms  of  the  hands  and  the  soles  of  the  feet,  but 
most  of  it  is  of  a  soft,  downy  variety,  which  is  not 
visible  without  close  observation. 

274.  The  Sebaceous  Glands. — There  are  certain 
small  glands,  situated  in  the  substance  of  the  derma, 
which  are  called  the  sebaceous* glands,  or  sometimes 
the  oil-glands.  They  are  composed  of  minute  sacs 
lined  with  epithelial  cells,  which  constantly  secrete 
and  pour  out  of  their  mouths  a  whitish,  tallow-like, 
fatty  substance.  Most  of  them  empty  into  the  hair- 
pits  or  follicles, f  as  they  are  called,  and  thence  their 
secretion  runs  along  the  hair,  and  out  on  the  sur- 
face of  the  body.  They  aid  in  keeping  the  hair  and 
skin  soft  and  flexible.  Sometimes  the  opening,  by 
which  the  secretion  of  the  gland  is  discharged, 
becomes  obstructed,  and  the  gland  still  goes  on 
secreting.  In  such  a  case,  a  swelling  makes  its  ap- 
pearance at  the  seat  of  the  trouble,  and  the  irrita- 
tion of  the  retained  secretion  causes  an  inflammation 
to  set  in,  which  continues  until  the  contents  of  the 
inflamed  sac  are  discharged,  or  let  out  by  the  prick 
of  a  needle.  This  is  the  cause  of  the  unsightly  lit- 
tle pimples  or  boils  which  occasionally  come  on  the 
end  of  the  nose,  and  give  rise  to  great  annoyance.:): 

*  Sebaceous,  from  the  Latin  sebum,  meaning  fat,  or  tallow. 

f  Fol'licle,  from  the  Latin  word  folliculus,  meaning  a  little  sack  or 
pouch. 

\  There  are  many  of  these  sebaceous  glands  about  the  end  of  the 
nose,  and  the  little  openings,  by  which  their  secretion  reaches  the  sur- 
face, often  become  obstructed  by  dirt,  so  that  the  secretion  accumulates 


222  ORGANS  OF  PROTECTION. 

275.  The  Sweat-Glands. — There  are  still  other 
glands  in  the  skin  which  have  a  very  important 
part  to  play  in  the  maintenance  of  life  itself.  These 
are  the  sweat-glands,  or  perspiratory  glands.  They 
are  situated  either  in  the  lowest  layer  of  the  derma 
or  in  the  loose  connective  tissue  just  beneath  it. 
The  mass  of  one  of  these  glands  is  convoluted — 
i.  e.,  it  is  made  up  of  a  long  tube,  rolled  about  and 
twisted  into  a  ball.  This  tube  is  lined  with  epithe- 
lial cells,  like  the  interior  of  all  glands,  and,  after 
leaving  the  convoluted  portion,  it  passes  in  quite 
a  direct  course  through  the  derma,  and  then  in 
a  spiral  course,  like  the  thread  of  a  corkscrew, 
through  the  epidermis,  on  the  surface  of  which  it 
opens.  If  one  of  these  little  glands  be  unrolled, 
and  its  tube  stretched  out,  it  is  found  to  be  about 
^  of  an  inch  in  length,  while  its  diameter  is  about 
j-J-o-  of  an  inch.  Notwithstanding  their  minute  size, 
however,  there  are  so  many  of  them  that  their  se- 
creting surface  is  enormous.  They  are  least  nu- 
merous on  the  neck  and  back,  where  there  are  417 
to  the  square  inch,  and  they  are  found  in  the  great- 
est numbers  on  the  palm  of  the  hand,  where  there 
are  no  less  than  2,700  of  them  to  the  square  inch. 
The  total  number  is  said  not  to  be  less  than  2,300,- 
000,  and  by  a  simple  calculation  it  will  be  found 
that  the  total  length  of  these  minute  tubes,  if  care- 
fully unrolled  and  placed  end  to  end,  would  be 
about  two  miles  and  a  half ! 

in  the  interior.  When  this  is  squeezed  out,  it  looks  like  a  small,  white 
worm,  the  dirt  at  the  outer  end  resembling  the  head.  Hence  the  term 
"black-heads."  To  be  sure,  there  are  sometimes  little  worms  found 
imbedded  in  this  secretion,  but  they  are  only  to  be  seen  with  the  mi- 
croscope. 


CHAPTER  II. 

FUNCTIONS   OF  THE   SKIN. — HYGIENE. 

276.  Effects  of  Pressure  on  the  Skin. — It  is  evi- 
dent, without  demonstration,  that  the  skin  protects 
the  parts  beneath  it.  In  the  performance  of  this 
function,  it  sometimes  resents  too  great  pressure,  or 
unequal  pressure,  from  outside.  In  such  cases  the 
skin  becomes  thicker  in  spots  where  the  pressure 
occurs.  If  the  epidermis  only  is  affected  in  such 
cases,  and  there  is  merely  an  increased  production 
of  epidermal  cells  from  beneath,  the  skin  becomes, 
as  we  say,  callous.  If,  however,  the  derma  be  affect- 
ed, the  papillae  become  enlarged  and  project  above 
the  surface,  warts  are  produced,  and,  where  both 
forms  of  growth  take  place,  we  have  corns.  Press- 
ure is  undoubtedly  not  the  only  cause  of  the  devel- 
opment of  these  unpleasant  diseases,  but  it  is  one 
cause.  But  the  origin  of  warts,  in  particular,  is 
generally  obscure. 

277.  Animal  Heat. — The  skin  also  has  an  impor- 
tant function  to  perform  in  maintaining  a  uniform 
temperature  in  the  body.  Every  one  knows  that  a 
living  body  is  warm.  Why  is  it  so?  There  has 
been  much  discussion  on  this  point,  and  many  theo- 
ries proposed  regarding  it.     When  oxygen  was  first 


224  ORGANS  OF  PROTECTION. 

discovered,  Lavoisier*  supposed  that  the  process  ot 
respiration  was  a  process  of  combustion ;  that  the 
oxygen  which  entered  the  lungs  in  the  air  united 
directly  with  the  carbon  in  the  venous  blood,  and 
produced  carbon  dioxide.  In  ordinary  flame,  this 
is  the  chemical  change  which  accompanies  combus- 
tion. The  oxygen  of  the  air  unites  with  the  carbon 
of  the  tallow  or  oil  and  produces  carbon  dioxide, 
the  hydrogen  of  the  oil  also  uniting  with  oxygen  to 
produce  water.  Thus  we  get,  as  a  result  of  com- 
bustion, a  disappearance  of  oxygen  and  a  produc- 
tion of  carbon  dioxide  and  water.  Now,  in  the  air 
which  passes  in  and  out  of  the  lungs,  we  find  the 
same  thing.  Oxygen  passes  in,  and  carbon  di- 
oxide and  water,  in  the  form  of  vapor,  come  out. 
What  more  natural,  then,  than  to  conclude  that 
respiration  was  combustion,  and  the  lungs  a  sort  of 
stove  by  which  the  heat  of  the  body  was  kept  up  ? 

It  was  soon  found,  however,  that  the  lungs  were 
no  warmer  than  the  rest  of  the  body,  and  particu- 
larly that  the  blood  contained  carbon  dioxide  be- 
fore it  reached  the  lungs,  and  took  away  free  oxygen 
from  them.  These  facts  showed  conclusively  that 
the  change  did  not  take  place  in  those  organs. 

The  great  chemist,  Liebig,f  then  changed  the  the- 

*  Antoine  Laurent  Lavoisier,  a  celebrated  French  chemist  (1743- 
1794).  He  first  discovered  the  composition  of  water,  and  invented  a 
chemical  nomenclature  which  lasted  for  more  than  fifty  years.  He  was 
guillotined  during  the  French  Revolution,  because,  twenty  years  before, 
he  had  been  a  tax-gatherer  under  the  monarchy. 

f  Baron  Justus  von  Liebig,  a  renowned  German  chemist  (1803- 
1873),  Professor  of  Chemistry  at  Munich.  He  was  the  greatest  chem- 
ist of  his  time,  made  many  practical  applications  of  chemistry  in  agricul- 
ture and  the  arts,  and  was  one  of  the  founders  of  the  science  of  organic 
chemistry. 


FUNCTIONS  OF   THE  SKIN— HYGIENE.    225 

ory,  by  supposing  that  the  combustion  took  place, 
not  in  the  lungs,  but  in  the  tissues  generally  through- 
out the  body,  and  this  theory  was  for  a  long  time  ac- 
cepted. It  is  now  giving  way,  however,  as  it  has 
been  found  that  many  other  chemical  processes,  be- 
sides the  union  of  carbon  and  oxygen,  give  forth 
heat,  and  that  the  amount  of  oxygen  inhaled  with 
the  breath  hardly  ever  corresponds  with  the  amount 
contained  in  the  carbon  dioxide  expired.  It  is  now 
considered  that  the  heat  of  the  body  is  the  result,  not 
of  one  class  of  chemical  phenomena,  but  of  all  the 
molecular  changes  and  combinations  which  are  con- 
stantly taking  place  in  all  parts  of  the  body. 

278.  Normal  Temperature  of  the  Human  Body. 
— The  temperature  natural  to  any  animal  is  found 
to  be  such  that,  if  the  blood  be  made  very  much 
cooler  or  very  much  warmer,  it  is  fatal  to  life.  The 
proper  temperature  of  the  interior  of  the  human 
body  is  about  ioo°  Fahr.  On  the  surface,  of  course, 
some  parts  are  cooler  than  others,  according  to  the 
degree  of  exposure  to  which  they  have  been  sub- 
jected. Physicians  usually  take  the  temperature  of 
patients  by  placing  the  bulb  of  a  thermometer  in 
the  armpit,  and  the  instrument  in  this  spot  gener- 
ally registers  about  98^°  Fahr.  The  normal  tem- 
perature often  varies  -J-°  or  i°  from  this  standard,  ac- 
cording to  the  time  of  day  or  night,  and  according 
to  the  sleeping  or  waking  condition  of  the  person. 

279.  Great  Variations  in  External  Temperature. 
— Now,  if  the  blood  be  cooled  much  below  this 
point,  say  down  to  8o°,  death  takes  place ;  equally 
so  if  it  be  heated  to  a  temperature  of  1130.  In  the 
former  case,  the  person  is  said  to  have  been  frozen, 
for  the  temperature  can  not  be  reduced  to  this  point 


226  ORGANS  OF  PROTECTION. 

unless  by  exposure  to  a  very  frigid  atmosphere ; 
and,  in  the  latter  case,  he  is  said  to  die  of  sunstroke, 
because  such  a  temperature  is  rarely  induced,  ex- 
cepting in  extremely  hot  weather. 

But  persons  are  often  exposed  to  a  temperature 
of  io°  or  20°  below  zero,  and  of  from  ioo°  to  1300 
above  zero.  The  latter  figures,  perhaps,  require 
a  word  of  explanation.  We  are  apt  to  think  of  the 
temperature  to  which  we  are  exposed  in  a  hot  sum- 
mer's day  as  the  same  which  we  find  registered  by 
a  thermometer  hanging  in  a  sheltered  spot.  This 
is  an  incorrect  way  to  estimate  it.  Many  of  us, 
perhaps  most  of  us,  spend  some  time  every  day  in 
the  direct  rays  of  the  sun,  and  it  is  no  uncommon 
thing  for  a  thermometer  placed  in  the  same  situa- 
tion to  register  1300.  How,  then,  are  we  enabled 
to  resist  such  extremes  of  cold  and  heat,  and  main- 
tain our  bodily  temperature  almost  unchanged  ? 

280.  Effect  of  Cold  on  the  Body.— When  the 
body  is  exposed  to  a  low  temperature,  and  the  sur- 
face is  being  continually  cooled  by  radiation,  the 
first  effect,  as  the  cold  reaches  the  tissues  just  un- 
der the  skin,  appears  to  be  a  stimulating  one ;  the 
processes  of  nutrition,  of  cell  destruction  and  for- 
mation, take  place  with  greater  rapidity,  and  there- 
fore more  food  is  required  to  supply  the  waste. 
We  all  know  that  in  cold  weather  our  appetites  are 
more  keen,  and,  if  we  digest  more,  we  must  waste 
more,  or  else  accumulate  material  in  our  bodies. 
This  latter  phenomenon  does  take  place  to  some 
extent,  and  most  persons  gain  flesh  during  cold 
weather.*     Now,  these  changes  in  nutrition,  with 

*  Cold  weather  produces  a  craving  for  fatty  foods.    The  Esquimaux 
eat  enormous  quantities  of  blubber.     Dr.  Hayes,  the  Arctic  explorer, 


FUNCTIONS  OF   THE  SKIN— HYGIENE.    227 

increased  activity,  give  rise  to  an  increase  of  tem- 
perature, and,  up  to  a  certain  point  of  exposure,  this 
increase  of  heat  is  sufficient  to  balance  the  increased 
radiation.  When  the  radiation  becomes  excessive, 
and  the  greatest  activity  of  the  bodily  functions  is 
insufficient  to  produce  enough  heat  to  compensate 
for  it,  the  blood  begins  to  grow  cool,  and  the  symp- 
toms of  drowsiness  and  stupor  come  on,  which  are 
the  precursors  of  death. 

281.  Effect  of  Heat  on  the  Body.— On  the  other 
hand,  when  the  temperature  is  high,  the  tendency 
to  the  accumulation  of  too  much  heat  in  the  body 
is  kept  down  partly  by  a  diminution  of  activity  in 
the  nutritive  processes,  and  partly  by  the  action  of 
the  perspiratory  glands.  In  hot  weather,  the  nu- 
tritive processes  go  on  much  more  slowly  than  in 
cold,  we  eat  much  less  food,  most  of  us  lose  flesh, 
and  the  production  of  animal  heat  in  the  interior 
of  the  body  is  thus  very  much  reduced.  But  this 
reduction  is  not  sufficient  to  guard  us  against  the 
harmful  effects  of  a  very  high  temperature.  If  cold 
becomes  too  great  to  be  resisted  by  the  ordinary 
forces  at  work  within  the  body,  we  put  on  addi- 
tional clothing,  build  ourselves  fires,  shelter  our- 
selves in  houses,  etc.,  and  thus  keep  warm.  But  in 
hot  weather,  if  we  had  no  perspiratory  glands,  we 
should  be  badly  off  indeed. 

282.  How  the  Temperature  of  the  Body  is  regu- 
lated.— The  way  in  which  these  glands  regulate  the 
temperature  of  our  bodies  is  by  covering  the  sur- 

states  that  his  men  often  drank  clear  oil  with  great  relish,  and  the 
Laplanders  are  said  to  be  fond  of  tallow-candles.  Even  in  our  own 
climate,  fried  articles  of  food,  which  contain  a  good  deal  of  fat,  are 
palatable  in  winter,  but  very  distasteful  in  warm  weather. 


228  ORGANS  OF  PROTECTION. 

face  of  the  skin  with  a  watery  fluid,  whose  evapora- 
tion continually  abstracts  heat.  Evaporation  con- 
sists in  the  change  of  a  liquid  into  vapor.  The 
evaporation  of  any  liquid  causes  a  diminution  of 
temperature  in  whatever  lies  in  contact  with  it. 
Liquids  which  evaporate  very  rapidly,  like  ether, 
produce  a  very  striking  sensation  of  cold,  and  may 
even  be  used,  in  the  form  of  spray,  to  freeze  a  por- 
tion of  the  body.  Now  when  the  surface  cf  the 
body  is  heated,  the  vaso-motor  nerves  are  some- 
what paralyzed,  and  an  unusual  flow  of  blood  takes 
place  to  the  capillaries  of  the  skin.  A  great  flow 
of  blood  to  a  gland  causes  an  increased  secretion, 
and  accordingly  the  perspiratory  glands  immedi- 
ately begin  to  pour  forth  their  peculiar  secretion. 
The  perspiration  is  composed  of  water  and  salts, 
containing  about  99^  per  cent  of  water.  This  water 
evaporates  rapidly,  and  abstracts  so  much  heat  that 
the  temperature  of  the  body  is  kept  at  its  normal 
standard. 

283.  Amount  of  Perspiration. — The  secretion  of 
the  perspiration  takes  place  constantly.  Under  or- 
dinary circumstances,  its  amount  is  so  small  that  it 
does  not  collect  in  drops,  but  evaporates  as  soon  as 
it  reaches  the  surface.  This  is  called  the  "  insen- 
sible perspiration,"  and  takes  place  at  all  times.  Al- 
though so  gradually  secreted  and  so  quickly  evap- 
orated as  to  be  unperceived  by  the  individual,  its 
daily  amount  is  surprisingly  large.  Lavoisier  and 
Seguin  have  found  it  to  be  a  little  less  than  two 
pounds.  This  amount  is  immensely  increased  when 
the  body  is  exposed  to  an  elevated  temperature,  and 
the  perspiration  begins  to  run  from  the  pores  in 
streams.     It  then  often  rises  to  the  amount  of  a 


FUNCTIONS  OF   THE  SKIN— HYGIENE.    229 

pound  an  hour,  and,  as  this  great  loss  of  fluid  from 
the  body  has  to  be  resupplied  from  without,  such 
excessive  perspiration  is  followed  by  excessive  thirst. 

284.  Exposure  to  Dry  Heat. — In  order  for  evap- 
oration to  take  place  rapidly,  the  air  must  be  dry 
enough  to  absorb  the  vapor  into  which  the  water 
passes.  If  the  air  be  very  dry,  and  contain  very 
little  water,  so  that  it  is  prepared  to  absorb  an  im- 
mense amount  of  it,  the  human  body  can  endure 
without  injury  an  incredibly  high  temperature. 
Human  beings  have  remained  in  ovens  heated  to  a 
temperature  of  from  3500  to  6oo°  Fahr.,  and  re- 
mained there  while  eggs  and  even  beefsteaks  were 
cooked  by  their  side.* 

285.  Exposure  to  Moist  Heat. — If,  on  the  other 
hand,  the  air  be  already  so  saturated  with  watery 
vapor  that  it  can  not  take  up  much  more  (for  its 
capacity  in  this  respect  is  limited),  any  great  rise  in 
temperature  causes  extreme  discomfort.  It  is  on 
account  of  this  difference  in  the  moisture  of  the 
atmosphere,  and  consequent  diminution  or  increase 
of  evaporation,  that  our  physical  comfort  varies  so 
much  on  different  days,  when  the  thermometer  reg- 
isters the  same  temperature.  For  this  reason,  also 
(the  moister  atmosphere),  a  temperature  of  850  is 
almost  unendurable  in  London,  while  in  New  York 
it  is  usually  borne  without  discomfort. 

*  "  The  workmen  of  the  sculptor  Chantrey  were  in  the  habit,  accord- 
ing to  Dr.  Carpenter,  of  entering  a  furnace  in  which  the  air  was  heated 
up  to  3500  "  (Dalton).  A  public  performer,  named  Chabert,  who  called 
himself  the  "  Fire-King,"  is  said  to  have  exposed  himself  to  a  tempera- 
ture of  6oo°,  and  remained  in  an  oven  heated  to  that  degree  while  a 
beefsteak  was  cooked  by  his  side.  In  such  experiments  care  has  to  be 
taken  that  no  metal,  or  other  good  conductor  of  heat,  comes  in  contact 
with  the  body,  for  if  it  does  it  will  cause  frightful  burns. 


230 


ORGANS  OF  PROTECTION. 


286.  Respiration  and  Absorption  through  the 
Skin. — There  is  also  a  certain  amount  of  what 
might  be  called  respiration  going  on  through  the 
skin — i.  e.,  it  has  been  shown,  by  inclosing  one  of 
the  limbs  in  an  air-tight  case,  that  the  contained  air 
loses  oxygen  and  gains  carbon  dioxide,  showing 
that  an  interchange  of  those  gases  takes  place 
through  the  skin,  as  well  as  through  the  lungs.* 
It  is  also  a  fact,  well  known  to  physicians,  that  the 
skin  possesses  the  property  of  absorbing  various 
substances  placed  in  contact  with  it.f 

The  skin  is  thus  seen  to  be  an  exceedingly  com- 
plex organ,  and  to  possess  many  very  important 
functions.  There  are  certain  peculiarities  attend- 
ing injuries  and  diseases  of  the  skin  which  have 
led  many  physiologists  to  think  it  has  important 
functions  not  yet  discovered.^ 

The  hygiene  of  the  skin  has  mainly  to  do  with 
the  questions  of  how  to  keep  it  cleansed  from  im- 
purities, and  how  to  regulate  its  temperature — i.  e., 
with  bathing  and  clotliing. 

*  The  amount  of  carbon  dioxide  thrown  off  by  the  skin  is  esti- 
mated at  about  one  thirtieth  of  that  exhaled  from  the  lungs. 

\  Medicines  are  sometimes  administered  by  rubbing  them  into  the 
skin.  Castor-oil  rubbed  over  the  stomach  will  produce  a  medicinal 
effect,  and  so  will  mercury.  Infants  who  were  too  much  exhausted  by 
disease  to  eat,  or  whose  stomachs  refused  to  retain  food,  have  been 
saved  from  death  by  rubbing  nutritive  substances,  oils,  etc.,  upon  the 
surface  of  the  body. 

X  When  the  surface  of  the  body  is  completely  covered  with  a  coat- 
ing impervious  to  air,  death  ensues  very  rapidly.  At  the  coronation 
of  Giovanni  de'  Medici  (1475-T521)  as  Pope  Leo  X,  a  little  boy  was 
covered  with  gold-foil  to  represent  a  cherub,  and  add  to  the  splendor 
of  the  ceremonies.  He  became  almost  immediately  ill,  however,  and, 
in  spite  of  all  that  was  done,  died  in  a  few  hours,  because  the  gold  and 
varnish  were  not  removed. 


FUNCTIONS  OF   THE  SKIN.— HYGIENE.     231 

287.  Necessity  of  cleansing  the  Skin. — The  im- 
purities on  the  surface  of  the  skin  come  mainly  from 
three  sources  :  1.  The  perspiration  contains  a  small 
amount  of  solid  matter,  mostly  mineral,  which  is 
deposited  upon  the  skin  and  left  there  as  the  water 
evaporates.  2.  The  fatty  secretion  of  the  sebaceous 
glands  is  constantly  being  poured  out  in  small  quan- 
tity, and  dries  upon  the  surface.  3.  The  epidermal 
scales  in  the  outer  layer  of  the  skin  are  being  con- 
tinually shed,  pushed  off,  as  it  were,  by  the  cells 
developing  under  them,  and  most  of  them  fall  away 
in  the  form  of  a  fine,  branny  dust,  which  clings  to 
the  under-clothing,  and  is  brushed  and  washed  from 
other  parts  of  the  body.  A  certain  amount  of  this 
refuse  epidermis  is  caught  in  the  drying  perspira- 
tion and  sebaceous  secretion,  and  so  remains,  as  it 
were,  glued  to  the  surface.  These  different  impuri- 
ties tend  to  choke  the  mouths  of  the  perspiratory 
and  sebaceous  glands,  and  prevent  their  free  action. 
The  surface  of  the  body  must  be  kept  free  from 
such  accumulations. 

Much  obscurity  has  been  unnecessarily  thrown 
around  the  subject  of  the  ordinary  bath.  The  rules 
regarding  it  are  in  reality  few  and  simple.  The  dis- 
cussions mainly  relate  to  the  time,  duration,  and 
temperature  of  the  bath,  and  the  results  may  be 
summed  up  thus  : 

288.  Effect  of  a  Cold  Bath.— The  first  effect  of  a 
cold  bath  is  to  produce  a  shock  to  the  nervous  sys- 
tem, resulting  in  the  contraction  of  the  blood-vessels 
at  the  surface  of  the  body.  This  shock  in  a  healthy 
person  is  soon  followed  by  a  reaction,  in  which  the 
heart  acts  with  more  vigor  than  usual,  and  the  con- 
tracted blood-vessels  are  again  filled   with  blood. 


232  ORGANS  OF  PROTECTION. 

The  surface  of  the  body  then  becomes  ruddy  or 
rosy,  and  a  pleasurable  glow  is  felt  by  the  bather. 
The  bath  should  end  while  this  glow  of  reaction 
continues,  for,  if  it  is  allowed  to  pass  away,  it  is 
succeeded  by  a  feeling  of  lassitude  and  depression, 
which  may  last  for  the  rest  of  the  day,  and  indicates 
a  certain  degree  of  exhaustion  of  the  nervous  sys- 
tem. The  after-glow  may  be  increased,  and  the 
good  effect  of  the  cold  bath  enhanced,  by  a  brisk 
rubbing  of  the  surface  with  the  hands  or  a  towel. 

289.  Effect  of  a  Warm  Bath.— The  first  effect 
of  a  warm  bath  is  to  dilate  the  superficial  blood- 
vessels and  cause  a  flow  of  blood  to  the  skin.  This 
produces  a  general  relaxation  of  the  pores  of  the 
glands,  tends  to  increase  their  activity,  and  in 
weakly  persons  there  is  slight  stimulation  of  the 
nervous  system.  After  such  a  bath,  the  skin  being 
full  of  blood  and  in  a  relaxed  condition,  exposure 
to  the  cold  air  is  dangerous,  and  the  bather  should 
not  go  out-of-doors  until  the  surface  of  the  body  is 
perfectly  dry,  and  any  feeling  of  languor  has  disap- 
peared. 

290.  Rules  for  Bathing.— Briefly  stated,  then, 
these  are  the  rules  for  guidance  in  the  bath  : 

Do  not  bathe  within  three  hours  after  a  meal,  as  the 
change  in  the  circulation  produced  by  the  change 
in  temperature  of  the  surface  of  the  body  interferes 
with  the  proper  distribution  of  blood  in  the  digest- 
ive organs. 

Do  not  bathe  in  cold  water,  if  you  have  found  by 
previous  trials  that  you  always  have  a  chilly  feeling  af- 
terzvard.  This  is  a  matter  to  be  determined  wholly 
by  personal  experience,  and,  when  any  person  finds 
that  a  particular  kind  of  bath  makes  him  uncom- 


FUNCTIONS  OF   THE  SKIN— HYGIENE.    233 

fortable  afterward,  it  is  the  part  of  prudence  to 
shun  it  thenceforth.  As  a  general  rule,  it  may  be 
stated  that  a  vigorous  person  will  feel  better  after  a 
cold  bath,  and  a  feeble  person  after  a  warm  one,  if 
not  too  prolonged. 

Do  not  remain  in  the  bath  too  long.  If  you  feel 
chilly  when  you  come  out,  the  bath  will  do  you 
more  harm  than  good.  As  a  general  rule,  from  ten 
to  fifteen  minutes  is  long  enough  for  a  warm  bath, 
and  five  minutes  for  a  cold  one. 

291.  Washing  the  Hands  and  Face. — The  hands 
and  face  are  washed  more  frequently  than  any  other 
part  of  the  body,  because  they  are  more  exposed 
and  become  dirty  sooner.  If  they  can  be  kept  clean 
with  water  alone,  soap  should  be  avoided,  because 
it  unites  with  the  fatty  matters  on  the  surface,  a  cer- 
tain amount  of  which  is  natural  and  necessary  to 
keep  the  skin  soft  and  pliable.  Soaps  that  contain 
an  excess  of  alkali  *  are  particularly  injurious,  be- 
cause they  not  only  remove  too  much  of  the  seba- 
ceous secretion,  but  irritate  the  surface  and  even 
produce  eruptions.  After  the  hands  have  been 
washed,  especially  in  cold  weather,  they  should  be 
carefully  and  thoroughly  dried  before  exposing 
them  to  the  cold  air.  It  is  the  neglect  of  this  pre- 
caution, together  with  the  excessive  use  of  soap, 
that  causes  "  chapping "  of  the  hands.  The  soap 
removes  the  fatty  matter  from  the  epidermis,  thus 
depriving  it  of  its  pliability,  and  the  water,  espe- 

*  Soap  is  made  by  boiling  fat  with  potash  or  soda  ;  the  former 
makes  soft  soap  and  the  latter  hard  soap,  such  as  is  commonly  used  in 
the  toilet.  If  the  proportions  of  these  ingredients  are  not  precisely 
right,  there  will  be  an  excess  of  one  of  them  in  the  product,  and  this 
excess  is  always  alkaline,  because  special  care  is  taken  to  neutralize  all 
the  fat.' 


234  ORGANS  OF  PROTECTION. 

cially  if  it  is  warm,  is  absorbed  to  a  certain  extent 
by  the  outer  cells  of  the  epidermis,  so  that  they  swell 
a  little  and  become  softer  than  before.  The  epider- 
mis thus  becomes  less  elastic  and  less  tenacious. 
If  it  is  suddenly  exposed  to  the  cold  while  in  this 
condition,  the  outer  layer  contracts  and  tears  apart, 
in  some  places  making  cracks,  which  often  extend 
down  to  the  derma,  and  give  rise  to  considerable 
suffering.  Then  fatty  matter  (grease,  vaseline,  etc.) 
has  to  be  supplied  to  take  the  place  of  the  natural 
secretion  that  has  been  so  unthinkingly  removed. 

To  keep  the  skin  of  the  faec  and  hands  smooth  and 
pliable,  therefore,  soap  should  be  used  sparingly,* 
and  they  should  be  thoroughly  dried  after  wash- 
ing. 

292.  Care  of  the  Scalp. — The  scalp  should  also  be 
kept  clean.  The  epidermis  is  shed  constantly  in 
this  region,  as  well  as  in  other  parts  of  the  body, 
and,  together  with  the  dried  sebaceous  secretion, 
causes  what  is  known  as  "  dandruff."  f  The  hair 
should  be  dressed  with  a  brush  that  is  not  stiff 
enough  to  scratch  the  scalp,  and  the  comb  should 
be  used  only  to  part  the  hair  and  disentangle  it, 
never  to  relieve  itching.  Constant  scratching  of 
the  scalp  increases  the  trouble  it  is  designed  to  re- 
lieve, and  makes  it  rough  and  inflamed,  just  as  the 
same  treatment  will  affect  the  back  of  the  hand  or 
the  cheeks.  It  is  well  to  wash  the  scalp  thoroughly 
with  cold  water  at  least  once  a  week,  drying  the 

*  The  highly-scented  toilet-soaps  are  often  made  of  rancid  fat,  and 
injure  the  skin.  The  best  soap  for  ordinary  use  is  the  white  Castile 
soap,  of  Spanish  or  Italian  manufacture,  which  is  made  of  sweet  olive- 
oil  and  not  perfumed. 

\  Extreme  degrees  of  dandruff  are  the  result  of  a  disease  of  the 
scalp,  and  are  often  difficult  to  cure. 


FUNCTIONS  OF   THE  SKIN— HYGIENE.    235 

hair  before  going  out-of-doors.  The  hair  of  girls 
should  never  be  cut,  if  it  is  possible  to  avoid  it,  as 
it  is  the  universal  testimony  that  it  never  grows  as 
long  after  cutting  as  if  it  is  left  alone. 

293.  Care  of  the  Nails. — The  finger-nails  should 
be  carefully  trimmed,*  but  never  cut  close  to  the 
flesh.  If  they  are  cut  too  short,  not  only  is  the  deli- 
cacv  of  touch  affected,  but  the  ends  of  the  fingers 
will  become  club-shaped  and  ugly.  The  flesh  about 
the  roots  and  sides  of  the  nails  should  not  be  allowed 
to  adhere  to  them,  as  it  is  pulled  along  and  stretched 
as  the  nail  grows,  and  produces  "  hang-nails."  The 
white  spots  which  often  appear  on  the  nails  are 
caused  by  slight  blows  on  the  root  of  the  nail  dur- 
ing its  formation,  and  therefore  are  most  common 
in  children  and  in  persons  whose  occupation  exposes 
their  hands  to  such  violence.  They  are  of  no  spe- 
cial importance. 

294.  Clothing. — The  object  of  clothing  is  to  main- 
tain an  equable  temperature  at  the  surface  of  the 
body.  For  this  purpose  the  best  material  to  be 
worn  next  the  skin  is  a  poor  conductor  of  heat. 
Woolen  material,  from  its  porous  texture,  conducts 
heat  very  poorly,  and  flannel  should  therefore  al- 
ways be  worn  next  the  body,  summer  and  winter. 
No  other  material  can  be  compared  with  it  for  pro- 
tecting the  surface  against  sudden  changes  of  tem- 
perature. Linen,  on  the  other  hand,  is  such  a  good 
conductor  of  heat,  that  its  use  next  the  skin  is 
absolutely  dangerous.  Cotton  is  intermediate  be- 
tween the  two.      As  for  the  outside  clothing,  that 

*  It  is  better  to  soften  the  nails  slightly  in  warm  water  before  cut- 
ting ;  otherwise  they  will  often  split  or  break  at  the  edge,  especially 
in  cold  weather. 


236  ORGANS  OF  PROTECTION. 

may  be  safely  left  to  be  decided  by  the  comfort 
and  taste  of  every  individual. 

The  clothing  that  has  been  worn  during  the  day 
should  be  entirely  removed  at  night  on  going  to 
bed.  The  under-clothing,  which  has  been  for  so 
many  hours  in  contact  with  the  surface  of  the  skin, 
is  more  or  less  loaded  with  the  matters  cast  off  by 
it,  and,  if  it  is  not  changed  daily,  should  at  least 
be  thoroughly  aired  during  the  night. 

A  shoe  that  can  not  be  worn  continuously  dur- 
ing the  waking  hours  from  the  time  it  is  first  put 
on,  should  not  be  worn  at  all.  The  habit  of  "  break- 
ing-in"  new  shoes  inevitably  results  in  distortion 
of  the  feet  and  the  development  of  corns.  High 
heels  are  also  bad,  because  the  weight  of  the  body 
drives  the  toes  down  into  the  narrow  end  of  the 
shoe,  and  causes  the  painful  and  unnecessary  affec- 
tion known  as  "  in-growing"  nails. 

Always  ivear,  therefore,  a  good  non-conductor  of  heat 
next  the  skin. 

Never  wear  any  article  of  dress  that  pinches,  for 
it  will  inevitably  result  in  distortion  or  disease,  or 
both,  especially  in  the  young,  whose  bones  are  yield- 
ing and  whose  organs  are  not  fully  formed,  and  need 
perfect  freedom  for  their  healthy  development. 


PART    VI. 
ORGANS  OF  PERCEPTION. 


CHAPTER   I. 

TOUCH— TASTE — SMELL. 

295.  Structure  of  the  Papillae.  —  The  sense  of 
touch  has  its  seat  in  the  papillae  of  the  skin.  The 
nerves,  on  entering  the  papillae,  end  in  certain  oval- 
shaped  bulbs,  which  are  very  small,  and  are  com- 
posed of  connective  tissue,  quite  firm  in  texture,  but 
containing  a  soft  material  at  the  center.  The  nerve, 
on  entering  this  bulb,  loses  its  medullary  substance 
(or  myelin),  and  only  the  axis-cylinder  is  continued 
into  the  center.  The  papillae  do  not  all  contain 
such  bulbs  or  corpuscles,  but,  as  they  are  found 
in  the  greatest  numbers  in  places  where  the  sensi- 
bility is  most  acute,  it  is  reasonable  to  suppose  that 
their  function  is  intimately  connected  with  the  sense 
of  touch. 

296.  The  Sense  of  Touch. — By  this  sense  we 
gain  our  knowledge  of  hardness  and  softness,  heat 
and  cold,  roughness  and  smoothness.  The  sensi- 
tiveness of  the  skin,  as  every  one  knows,  varies  very 
much  in  different  parts  of  the  body,  and  attempts 
have  been  made  to  invent  some  means  of  measuring 
accurately  the  perfection  of  this  sense.     The  most 


238  ORGANS  OF  PERCEPTION. 

usual  method  is  to  apply  the  points  of  a  pair  of 
compasses  to  various  spots  on  the  surface  of  the 
body,  and  see  at  what  distance  apart  the  two  points 
can  be  perfectly  perceived  to  be  two  and  not  one. 
At  the  tips  of  the  fingers  they  can  be  separately 
distinguished  when  only  one  eighteenth  of  an  inch 
apart,  while  at  the  small  of  the  back  they  must  be 
separated  to  a  distance  of  nearly  two  inches  before 
they  will  cease  to  seem  one  point.  Between  these 
extremes  there  are  many  intermediate  grades  of 
sensation.* 

297.  Deception  by  the  Senses. — It  is  a  remark- 
able fact  that  the  extremes  of  any  kind  of  sensation 
can  not  readily  be  distinguished  from  each  other. 
A  piece  of  iron  at  a  white-heat  and  a  frozen  solu- 
tion at  yo°  below  zero  will  produce  much  the  same 
sensation  in  the  part  touching  them.  But  it  is  not 
so  familiar  a  fact  that,  after  all,  the  conscious  sense 
really  lies,  not  in  the  termination  of  the  nerve,  but 
in  the  nerve-center  which  receives  the  impulse  from 
it,  and  that,  if  this  be  out  of  order,  the  sense  may  be 
deceptive.  This  fact  of  our  liability  to  be  deceived 
by  our  senses  applies  to  all  of  them — the  sense  of 
touch  as  well  as  to  others.  A  single  illustration 
will  suffice.  It  might  seem  as  if  any  person  would 
be  able  to  determine  by  his  feelings  whether  he 
were  hot  or  cold,  and  yet  it  is  well  known  to  physi- 
cians that,  in  the  chill  of  fever  and  ague,  when  the 
sufferer,  with  blue  lips  and  chattering  teeth,  wants 

*  The  most  delicately  sensitive  part  is  the  tip  of  the  tongue,  where 
the  two  points  are  distinguished  when  only  one  thirtieth  of  an  inch 
apart.  As  every  one  knows,  a  fine  hair,  which  can  not  be  felt  by  the 
finger,  or  only  with  the  greatest  difficulty  and  uncertainty,  is  clearly 
perceived  by  the  tongue. 


TO  UCH—  TASTE— SMELL. 


239 


to  be  covered  deep  with  blankets,  his  temperature 
by  the  thermometer  is  much  higher  than  in  health, 
often  running  up  to  1060  Fahr.* 

298.  The  Special  Senses. — The  special  senses  are 
all  modifications  of  the  sense  of  touch,  and  were 
probably  developed  out  of  it.  They  differ,  how- 
ever, from  it,  and  from  one  another,  in  the  fact  that 
in  each  a  special  kind  of  sensation  is  roused  in  re- 
sponse to  whatever  form  of  stimulus.  Any  stimu- 
lus to  the  retina  of  the  eye,  for  example,  produces 
only  the  sensation  of  light — no  matter  whether  it  be 
light,  or  a  blow,  or  an  electric  current — and  so  with 
the  other  special  senses  (excepting  that  of  taste,  as 
hereafter  mentioned).  In  the  eye  and  the  ear,  the 
apparatus  for  the  special  appreciation  of  stimuli 
forms  a  highly  complicated  and  delicate  mechan- 
ism. In  the  description  of  these  special  senses,  we 
shall  begin  with  the  one  which  is  least  removed 
from  the  sense  of  touch,  and  end  with  the  one  in 
which  sense-perception  is  the  most  highly  devel- 
oped. 

299.  The  Tongue.  —  The  sense  of  taste  differs 
less  from  ordinary  sensibility  than  any  of  the  other 
senses.  It  is  located  chiefly  in  the  tongue,  but  it 
has  been  found,  by  careful  experiments,  that  we 
can  perceive  the  flavor  of  substances  also  with  the 
soft  palate  and  a  small  portion  of  the  throat.  The 
tongue  is  a  muscular  organ  of  great  mobility,  and  is 
supplied  with  three  nerves  from  the  brain.     One  of 

*  An  easy  way  to  satisfy  one's  self  of  the  deceptive  nature  of  our 
sensations,  and  of  the  fact  that  they  must  often  be  corrected  by  the 
judgment,  is  this  :  Put  one  hand  into  cold  water,  and  the  other  into 
warm  ;  take  them  out  quickly,  and  plunge  them  both  into  water  a  little 
cooler  than  the  warm  water  just  used  ;  it  will  be  found  that  this  water 
will  seem  cold  to  one  hand  and  warm  10  the  other. 


240  ORGANS  OF  PERCEPTION. 

these  nerves  presides  over  its  motions,  while  the 
other  two  are  sensitive  nerves,  one  of  which  is  dis- 
tributed to  the  anterior  two  thirds  of  the  surface  of 
the  organ,  and  the  other  to  the  posterior  portion 
(Fig.  65).  The  exact  method  in  which  these  nerves 
terminate  is  not  known,  but  the  surface  of  the  tongue 


Fig.  65. — Diagram  showing  the  distribution  of  the  nerves  of  taste  in  the 

tongue. 

is  covered  with  small  papillae,  which  can  be  easily 
seen  with  the  naked  eye,  and  the  delicate  extremi- 
ties of  the  nerves  are  known  to  terminate  in  these 
papillae.  It  is  well  known  that  no  substance  can  be 
perceived  by  the  taste  unless  it  is  soluble,  and  this 
renders  it  almost  certain  that  the  matter  tasted 
comes  into  actual  contact  with  the  end  of  the 
nerve. 

300.  The  Sense  of  Taste. — The  nerves  of  taste, 
in  distinction  from  most  nerves  of  special  sense, 
also  convey  sensation  like  the  nerves  of  general 
sensibility.  This  fact  makes  it  a  little  difficult  to 
distinguish  between  things  felt  by  the  tongue  and 
things  tasted.  It  is  considered  by  many  that  there 
are  in  all  only  four  modifications  of  the  sense  of  taste, 
viz.,  sweetness,  sourness,  saltness,  and  bitterness.     To 


TOUCH— TASTE— SMELL.  241 

these  qualities,  or  savors,  others  add  such  savors 
as  alkaline,  styptic,  etc.,  which  are  compound  sen- 
sations, and  it  is,  to  say  the  least,  very  doubtful 
whether  they  should  be  classed  as  distinct  savors. 
Qualities  which  are  really  the  result  of  feeling,  and 
not  of  taste,  although  perceived  by  the  tongue  and 
palate,  are  pungency,  starcliiness,  piquancy,  oiliness,  etc. 
Another  source  of  error  in  estimating  savors  lies  in 
the  fact  that  there  is  a  communication  between  the 
nose  and  mouth  through  the  throat.  It  is  some- 
times very  hard  to  distinguish  between  what  we 
perceive  by  the  sense  of  smell  and  what  we  taste. 
This  is  in  some  degree  the  case  with  liquids  which 
have  an  aroma  or  bonqnet,  but  it  may  be  shown  that 
the  aroma  is  perceived  entirely  by  the  sense  of  smell, 
by  closing  the  nostrils  while  tasting  the  aromatic 
substance.  It  will  then  be  found  that  the  aroma 
disappears,  although  the  communication  between 
the  nose  and  throat  still  remains  open.  The  reason 
for  this  will  be  explained  under  the  section  describ- 
ing the  sense  of  smell. 

301.  Peculiarities  of  the  Sense  of  Taste. — It  has 
been  stated  that  the  front  and  back  part  of  the 
tongue  are  supplied  by  different  nerves.  This  state 
of  things  gives  rise  to  a  curious  phenomenon,  viz., 
that  certain  substances  have  a  decidedly  different 
taste  when  placed  on  one  part  of  the  tongue  from 
what  they  have  on  the  other.  A  few  examples  of 
this  will  suffice  : 

If  potassium  chloride  be  put  upon  the  anterior  por- 
tion of  the  tongue,  it  tastes  saltish,  but  on  the  poste- 
rior, szceetish.  Sodium  sulphate,  on  the  anterior  portion, 
is  salt,  on  the  posterior,  bitter.  Alum,  on  the  anterior 
surface,  tastes  acid  and  styptic,  while  on  the  posterior, 


242  ORGANS  OF  PERCEPTION. 

it  has  a  decidedly  sweetish  taste,  with  no  acid  qual- 
ity whatever. 

The  sense  of  taste  persists  for  a  short  time  after 
the  substance  tasted  is  removed.  This  is  probably 
because  the  portion  of  the  substance  which  pene- 
trated the  mucous  membrane  and  affected  the  nerve 
has  not  all  been  taken  up  and  carried  away  by  the 
circulation.  For  this  reason,  it  is  impossible  to  ap- 
preciate the  true  savor  of  different  substances  by 
tasting  them  in  rapid  succession.  The  impression 
made  by  the  first  should  be  allowed  to  disappear, 
and  only  remain  in  the  memory,  before  the  sec- 
ond is  tasted.  This  only  applies  to  delicate  flavors. 
Where  the  flavors  are  coarse  and  pronounced,  the 
slight  masking  of  one  by  the  other  often  inter- 
feres very  little  with  a  correct  judgment  of  their 
character. 

The  flavor  of  any  substance  is  perceived  in  ex- 
act proportion  to  the  amount  of  surface  affected  by 
it.  So  we  see  connoisseurs  in  wine  smacking  their 
lips  and  pressing  their  tongues  against  the  roof  of 
the  mouth,  the  better  to  appreciate  the  flavor,  by 
spreading  the  liquid  over  a  larger  surface.  The 
use  of  this  sense  in  the  detection  of  impure  and  un- 
wholesome food  has  already  been  referred  to.  In 
addition  to  this  function,  it  affords  us  great  physical 
pleasure,  although  it  is  generally  thought  to  be  of 
a  low  order. 

The  sense  of  taste,  like  that  of  touch,  requires 
actual  contact  with  the  substances  tasted,  and  can 
give  us  no  knowledge  respecting  substances  at  a 
distance  from  our  bodies.  We  now  come  to  a  sense 
which  is  a  step  higher  in  the  scale,  for  it  gives  us 
knowledge  of  substances  at  a  distance,  and  it  does 


TO  UCH—  TASTE—SMELL. 


243 


this  by  means  of  material  emanations  which  often 
can  not  be  detected  in  any  other  way. 

302.  The  Sense  of  Smell. — The  sense  of  smell 
resides  in  the  mucous  membrane  lining  the  upper 
portion  of  the  cavity  of  the  nose.  This  portion  of 
membrane  is  supplied  by  the  olfactory  nerve,  which 
does  not  convey  ordinary  sensation,  as  do  the  nerves 
of  taste,  but  carries  to  the  brain  only  the  special 
sensation  of  smell.  The  nerve  is  distributed  to  the 
upper  third  of  the  nasal  passages,  and  the  rest  of 
the  interior  of  the  nose  is  supplied  by  nerves  of 
ordinary  sensation  (Fig.  66). 

The  amount  of  any  substance  required  to  affect 
the  sense  of  smell  is  inconceivably  minute.     There 


Fig.  66. — The  interior  of  the  left  nasal  passage.  The  fan-like  expansion  of 
nervous  fibers  is  the  olfactory  nerve.  The  other  nerves  shown  are  nerves 
of  ordinary  sensation. 

is  no  chemical  or  physical  means  known  by  which 
it  can  be  detected  in  many  cases.  A  grain  of  musk 
will  perfume  a  room  for  months,  and  lose  nothing 
apparently  in  weight. 


244 


ORGANS  OF  PERCEPTION. 


In  order  to  affect  the  sense  of  smell,  the  odorous 
air  must  be  drawn  through  the  nose.  If  the  air 
in  the  nasal  passages  remains  stationary,  we  smell 
nothing.  This  is  the  reason  why  closing  the  nostrils 
prevents  our  appreciating  aromatic  substances  in  the 
mouth.  For  this  reason,  also,  we  sniff  at  whatever 
has  a  delicate  or  faint  odor,  and,  by  increasing  the 
rapidity  of  the  air-current  through  the  nose,  we  add 
to  our  appreciation  of  the  odor.*  This  is  very  no- 
ticeable in  the  lower  animals. 

It  is  necessary  to  distinguish  between  substances 
which  really  affect  the  sense  of  smell  and  those 
which  merely  irritate  the  mucous  membrane.  Many 
substances  affect  both  senses — that  of  smell  and  that 
of  general  sensibility.  Pepper,  for  instance,  has  a 
clearly  distinguishable  and  peculiar  odor  of  its  own, 
which  is  appreciated  by  the  olfactory  nerve,  and  it 
also  irritates  the  nerves  of  general  sensibility.  Am- 
monia, if  pure,  is  merely  an  irritant,  and  has  no 
proper  odor  of  its  own. 

303.  Relative  Acuteness  of  the  Sense  of  Smell. — 
The  sense  of  smell  among  civilized  persons  is  not 
educated,  and  is  rather  defective.  Among  savages 
it  is  much  more  acute.  Humboldt  states  that  cer- 
tain South  American  Indians  can  detect  the  ap- 
proach of  a  stranger,  in  a  dark  night,  by  the  sense 
of  smell,  and  will  also  tell  whether  he  is  a  white 
man,  an  Indian,  or  a  negro.  But  the  lower  animals 
far  surpass  man  in  this  as  well  as  in  most  other 
senses.     The  keenness  of  the  dog's  scent  is  pro- 

*  The  distribution  of  the  olfactory  nerve  in  the  upper  part  of  the 
nose  also  makes  it  necessary  to  sniff  at  faint  odors,  for  otherwise  the 
air  containing  them  might  pass  through  the  lower  passages  of  the  nose 
into  the  throat,  without  reaching  the  nerve  of  smell. 


TOUCH—TASTE— SMELL.  245 

verbial,  and  he  depends  much  more  upon  his  sense 
of  smell,  for  recognition  of  his  master,  than  on  his 
sense  of  sight. 

The  sense  of  smell,  like  the  sense  of  taste,  acts 
as  a  sentinel  to  guard  against  the  introduction  of 
improper  food  into  our  stomachs.  It  also  warns 
us  of  impurities  in  the  air.  After  long  exposure, 
however,  to  a  particular  odor,  the  sense  appears  to 
become  blunted,  and  that  even  when  the  odor  is  a 
peculiarly  disagreeable  one.  It  seems  as  if,  when 
its  warnings  came  to  be  disregarded,  it  ceased  to 
give  any  more. 

The  sense  of  smell  appreciates  a  great  number 
of  distinct  odors,  and  from  delicate  and  fragrant 
ones  we  receive  a  great  deal  of  pleasure.  This 
sense,  undoubtedly,  occupies  a  higher  plane  than 
the  sense  of  taste,  and  a  delight  in  pleasant  per- 
fumes marks  a  higher  sense  of  aesthetic  gratification 
than  a  devotion  to  the  pleasures  of  the  table. 


CHAPTER   II. 

HEARING. 

304.  The  Sense  of  Hearing. — As  we  ascend  in 
the  scale,  we  come  to  a  sense  which  does  not  in- 
form us  of  what  is  taking  place  in  the  world  out- 
side of  us,  by  actual  contact  with  matter,  like  the 
senses  of  touch  and  taste ;  nor  by  contact  with 
emanations  from  matter,  like  the  sense  of  smell ; 
but  impressions  are  produced  upon  it  by  means  of 
motion  in  the  atmosphere  which  surrounds  us. 
This  is  the  sense  of  hearing.  Every  movement  of 
every  form  of  matter  gives  rise  to  waves  or  vibra- 
tions in  the  air,  which  lies  in  contact  with  the  mov- 
ing substance.  These  atmospheric  waves  are  re- 
ceived, and  the  impression  made  by  them  is  trans- 
mitted to  the  brain  by  a  special  apparatus. 

305.  The  External  Ear. — The  ear  (Fig.  6y)  is 
usually  described  by  anatomists  as  consisting  of 
three  divisions — the  external  ear,  the  middle  ear,  and 
the  internal  ear.  The  appearance  of  the  external 
ear  is  familiar  to  all.  It  has  a  somewhat  shell-like 
form,  has  numerous  ridges  and  hollows,  and  is  com- 
posed principally  of  cartilage  covered  with  skin. 
This  external  ear  serves  to  collect  the  waves  of 
sound,  and  direct  them  toward  the  internal  parts. 
In  animals  this  organ  is  very  movable,  and,  during 


HEARING. 


247 


their  waking  hours,  is  generally  in  motion,  to  catch 
sound  from  various  directions.     In  the  human  be- 


FlG.  67. — Section  of  the  ear,  showing  the  relative  positions  of  the  external, 
middle,  and  internal  ear. 


ing  there  are  three  small  muscles  attached  to  the 
external  ear — one  behind,  one  above,  and  one  in 
front.  These  muscles,  however,  are  practically  use- 
less, and  very  few  persons  have  any  voluntary  con- 
trol over  them.  Those  who  do,  can  cause  the  mus- 
cle in  the  rear  to  contract,  and  move  the  ear  slightly 
backward,  but  the  motion  is  limited,  and  answers 
no  purpose. 

306.  The  Middle  Ear. — From  the  external  ear  a 
canal  passes  directly  inward,  toward  the  interior  of 
the  skull,  for  a  distance  of  about  an  inch  and  a 
quarter.  At  its  inner  extremity  it  is  closed  by  a 
thin  membrane,  called  the  membrane  of  the  tympa- 
num, or  the  drum  of  the  ear ;  and  on  the  other  side 
of  this  membrane  is  a  small  cavity  in  the  bone,  about 


248  ORGANS  OF  PERCEPTION. 

a  third  of  an  inch  long,  a  quarter  of  an  inch  in  height, 
and  a  sixth  of  an  inch  wide,  called  the  tympanum*  or 
middle  car.  The  membrane  of  the  tympanum  is 
stretched  like  the  head  of  a  drum,  and  answers  some- 
what the  same  purpose.  Upon  this  membrane  the 
waves  of  air  strike,  causing  it  to  vibrate ;  and  this 
vibration  of  the  membrane  is  the  first  step  toward 
bringing  the  air-waves,  or  the  impulse  given  by  them, 
into  contact  with  the  nerve  of  hearing.  And  here 
we  remark  that,  in  order  for  the  vibration  of  a  mem- 
brane to  be  perfect,  the  air  on  both  sides  of  it  must 
be  of  the  same  degree  of  density  during  the  vibra- 
tion. In  the  common  drum  this  is  provided  for  by 
having  a  hole  in  the  side,  to  allow  free  passage  for 
the  air  in  and  out.  In  the  cavity  of  the  middle  ear 
it  is  provided  for  by  a  short  tube,  called  the  Eusta- 
chian f  tube,  leading  into  the  throat.  This  tube  is 
about  an  inch  and  a  half  or  two  inches  long,  and, 
for  perfect  hearing,  it  is  necessary  that  the  air 
should  pass  in  and  out  through  it  with  freedom. 

307.  The  Bones  of  the  Ear. — In  the  cavity  of  the 
middle  ear  is  a  chain  of  minute  bones,  three  in  number, 
which  altogether  only  weigh  a  few  grains.  One  of 
them  is  attached  to  the  membrane  of  the  tympanum, 
another  is  attached  to  another  membrane  stretched 
in  drum-like  form  across  a  small  hole  on  the  oppo- 
site side  of  the  middle  ear,  and  the  third  unites  the 
other  two.  These  small  bones  have  very  minute 
muscles  attached  to  them  in  such  a  way  that  by  their 
contraction  or  relaxation  the  bones  are  made  to  as- 
sume slightly  different  positions,  and  the  membranes 

*  Tympanum,  a  Latin  word  meaning  drum. 

\  Etistd chian,  from  Bartolomeo  Eustachi,  a  celebrated  Italian  anat- 
omist (died  1574),  who  first  described  it. 


HEARING.  249 

to  which  they  are  attached  are  made  more  or  less 
tense,  and  therefore  more  or  less  sensitive  to  sounds. 
It  is  probable  that  these  muscles  are  somewhat  un- 
der the  control  of  the  will,  and  that  some  of  the 
effort  of  which  we  are  conscious  when  we  strain  our 
attention  to  detect  a  faint  sound,  is  due  to  their 
active  contraction. 

308.  The  Internal  Ear. — The  second  membrane 
above  spoken  of,  which  is  smaller  than  the  mem- 
brane of  the  tympanum,  closes  the  passage  between 
the  middle  and  internal  ears.  The  internal  ear  or 
labyriyith  is  exceedingly  complicated,  and  the  func- 
tions of  its  parts  are  not  yet  well  understood.  The 
difficulties  of  investigation  are  immense,  partly  on 
account  of  the  minuteness  of  the  organs  and  partly 
because  they  are  situated  so  deeply  in  the  bones  of 
the  skull  and  are  so  near  the  brain.  It  is  sufficient 
to  say  that  the  internal  ear  is  made  up  of  many 
winding  channels  and  spiral  tubes,  which  go  by  the 
names  of  the  coclilca,  the  semicircular  canals,  and  a 
cavity  called  the  vestibule,  with  which  the  others 
communicate,  All  these  passages  are  filled  with  a 
watery  fluid,  and  on  their  walls  and  through  their 
interiors  are  distributed  the  filaments*  of  the  nerve 
of  hearing,  the  auditory  nerve.  As  has  been  said,  the 
cavity  of  the  vestibule  is  separated  from  that  of  the 
middle  ear  by  a  thin  membrane,  to  which  one  of 
the  bones  of  the  middle  ear  is  attached.  Thus,  any 
vibration  or  impulse  imparted  to  this  membrane 
produces  a  corresponding  pressure  on  the  nerve  of 
hearing,  through  the  medium  of  the  watery  fluid 
which  fills  all  parts  of  the  internal  ear. 

309.  Recapitulation. — Thus  the  air-waves  enter- 

*  Filaments,  small,  delicate,  thread-like  fibers. 


250 


ORGANS  OF  PERCEPTION. 


ing  the  external  ear  strike  upon  the  membrane  of 
the  tympanum,  and  put  it  in  vibration.  These  vi- 
brations are  communicated  through  the  chain  of 
bones  to  the  inner  membrane,  which  is  also  made 
to  vibrate.  These  vibrations,  again,  are  communi- 
cated to  the  watery  contents  of  the  internal  ear, 
and  they  in  turn  press  directly  upon  the  extremities 
of-  the  auditory  nerve,  which  conveys  the  impulse 
to  the  brain.     And  in  this  way  we  hear  sounds. 

310.  Different  Qualities  of  Sound. — When  we 
hear  sounds,  we  distinguish  many  different  quali- 
ties in  them,  such  as  pitch,  quality,  timbre,  degree, 
etc.  These  differences  mainly  depend  upon  the 
different  length,  rapidity,  height,  and  character  of 
the  air-waves.  They  are  perceived,  in  a  greater  or 
less  degree,  by  every  person,  but  the  ease  and  ac- 
curacy with  which  they  are  appreciated  may  be  in- 
creased by  education.  The  appreciation  of  musical 
sounds,  for  instance,  may  be  immensely  increased 
by  practice  and  proper  training. 

311.  Determination  of  the  Source  of  Sound. — 
Besides  the  perception  of  the  foregoing  differences 
in  sounds,  which  is  partly  the  result  of  natural  en- 
dowment and  partly  that  of  training,  there  is  an- 
other fact  with  regard  to  sound  which  has  given 
rise  to  considerable  discussion.  It  is  the  power  we 
have  of  determining  with  more  or  less  accuracy  the 
locality  from  which  a  sound  comes.  Some  physi- 
ologists have  supposed  that,  as  the  semicircular  ca- 
nals, three  in  number,  are  always  placed  at  different 
angles,  they  serve  in  some  way,  not  easily  explained, 
to  indicate  to  us  the  direction  from  which  the  air- 
waves come*     This  view  has  been  supported  by 

*  It  has  been  lately  suggested  that  the  semicircular  canals  have 


HEARING. 


251 


arguments  of  some  plausibility,  but  it  is  now  the 
accepted  view  that  our  knowledge  of  the  direction 
and  distance  of  the  source  of  any  sound  is  the  re- 
sult of  past  experience.  We  judge  partly  by  the 
loudness  of  a  familiar  noise,  partly  by  the  greater 
impression  on  one  ear  than  on  the  other,  partly  by 
the  difference  in  the  sound  when  we  turn  the  head 
a  little  one  way  or  the  other,  the  direction  of  the 
wind,  and  a  hundred  other  influences,  which  have 
become  a  part  of  our  experience.  If  we  can  not, 
for  any  reason,  use  enough  of  these  methods,  we 
find  ourselves  unable  to  locate  even  a  loud  and  dis- 
tinct sound  ;  e.  g.,  it  is  very  difficult  to  tell  in  what 
part  of  a  closed  room  to  look  for  a  chirping  cricket. 
312.  Ventriloquism. — The  art  of  ventriloquism  de- 
pends upon  an  adroit  use  of  these  methods  in  such 
a  way  as  to  deceive.  The  ventriloquist  slyly  robs 
us  of  all  the  means  which  generally  serve  us  to 
detect  the  origin  of  a  sound.  He  speaks  without 
moving  his  lips  ;  he  modulates  his  voice  so  that  it 
appears  to  come  from  a  distance,  on  account  of  its 
faintness ;  he  calls  the  attention  of  the  spectator, 
either  by  word  or  by  gesture,  to  the  point  from 
which  he  wishes  him  to  expect  the  sound,  and 
makes  clever  use  of  the  slight  shades  in  timbre  and 
pitch,  which  all  of  us  can  distinguish,  but  which  it 
requires  great  skill  and  practice  to  reproduce  as 

something  to  do  with  the  sense  of  direction,  and  with  the  preservation 
of  the  bodily  equilibrium.  It  has  been  found  that,  when  they  are  cut  in 
a  pigeon,  the  bird  sprawls  about  and  seems  incapable  of  co-ordinating 
its  movements.  There  is  a  disease  of  these  organs,  called  Meniere's 
disease,  from  the  man  who  first  described  it,  in  which  giddiness,  as  well 
as  deafness,  is  a  prominent  symptom.  It  is  probable  that  the  frequent 
attacks  of  vertigo,  with  increasing  deafness,  from  which  Dean  Swift 
suffered,  were  caused  by  this  disease. 


252  ORGANS  OF  PERCEPTION. 

professors  of  this  art  are  able  to.  The  common 
idea  that  a  man's  voice  can  actually  be  projected 
or  thrown  into  a  spot  twenty  feet  from  his  larynx 
is  the  idea  of  pure  ignorance,  and,  as  soon  as  one 
understands  the  mechanism  of  the  voice,  is  seen  to 
be  as  impossible  as  for  any  one  to  see  through  a 
solid  stone  wall,  a  thick  envelope,  a  book-cover,  or 
anything  else  through  which  no  light  can  pass. 

313.  Care  of  the  Ear. — The  ear  is,  in  almost  all 
its  parts,  a  very  delicate  organ,  but,  excepting  the 
external  ear,  it  is  so  deeply  set  in  bone  that  it  is 
not  very  liable  to  injury ;  and  yet  neglect  of  the 
organ  or  ignorant  tampering  with  it  may  result  in 
permanent  and  irreparable  harm.  The  tube  leading 
inward  from  the  external  ear,  called  the  external 
auditory  ca?ial,  is  sometimes  entered  by  insects.  Its 
walls  are  moistened  by  a  peculiar  secretion,  called 
"  wax,"  produced  by  small  glands  just  beneath  the 
skin  which  lines  it.  This  wax  is  somewhat  sticky, 
and  is  intensely  bitter,  and,  together  with  certain 
short  hairs  near  the  outlet  of  the  canal,  serves  to 
protect  the  membrane  of  the  tympanum  from  the 
inroads  of  insects.*  The  wax  has  sometimes  a 
tendency  to  accumulate  and  interfere  with  the 
hearing ;  and  some  persons  are  in  the  habit  of 
cleaning  their  ears  with  ear  -  scoops.  This  is  an 
exceedingly  dangerous  practice,  and  can  not  be 
too  severely  condemned.  The  ear  is  a  delicate  or- 
gan, and  must  be  treated  delicately  by  a  person 
who  thoroughly  understands  its  anatomy. 

314.  Danger  of  Colds  in  the  Head. — The  dan- 

*  Insects  can  sometimes  be  coaxed  out  of  the  ear  by  holding  a  light 
in  front  of,  and  quite  near,  the  external  opening.  They  are  attracted 
by  the  light,  as  moths  are,  and  turn  round  and  crawl  toward  it. 


HEARING.  253 

ger  of  injury  to  the  hearing  apparatus  through  the 
Eustachian  tube  is  principally  from  inflammation. 
Colds  in  the  head  almost  always  affect  the  hearing 
in  some  degree,  on  account  of  the  swelling  of  the 
membrane  around  the  mouth  of  the  tube.  But  the 
inflammation  may  not  stop  at  this  point.  It  some- 
times travels  along  the  tube  to  the  middle  ear,  and 
when  the  exceedingly  delicate  mucous  membrane  of 
the  middle  ear  becomes  affected,  there  is  usually 
more  or  less  permanent  impairment  of  the  sense  of 
hearing.  The  little  chain  of  bones  becomes  stiffened 
by  the  disease,  just  as  an  elbow  or  knee  does  after 
an  attack  of  rheumatism,  and  so  they  conduct  the 
vibrations  of  the  membrane  of  the  tympanum  with 
less  force  and  accuracy.  On  the  slightest  indication, 
therefore,  of  inflammation  of  the  Eustachian  tube, 
as  indicated  by  unusual  dullness  of  hearing,  during 
an  acute  catarrh  of  the  nose  or  throat,  a  physician 
should  be  consulted.  The  process  just  described 
gives  rise,  in  the  climate  of  New  York,  to  about 
two  thirds  of  all  the  cases  of  deafness. 

12 


CHAPTER  III. 

SIGHT. 

315.  The  Sense  of  Sight. — We  now  come  to  the 
highest  and  most  perfect  of  all  the  senses,  that  of  sight. 
The  four  senses  previously  considered  all  depend 
on  material  contact,  in  a  greater  or  less  degree,  for 
their  appreciation  of  the  external  world.  Even  the 
last  sense  considered,  that  of  hearing,  depends  on 
contact  with  waves  in  the  air,  which  is  a  form  of 
matter,  although  attenuated.  But  we  now  have  to 
do  with  an  organ  which  perceives  external  objects 
through  the  intervention  of  light,  and  light  is  some- 
thing which  can  not  be  felt  or  weighed,  or  detected 
in  any  other  way  than  by  sight.  There  have  been 
many  theories  regarding  the  nature  of  light,  but 
the  one  most  in  favor  at  the  present  day  is  the  wave 
theory,  or  7tJidnlatory  theory,  so  called. 

316.  The  Nature  of  Light. — According  to  this 
theory,  the  universe  is  pervaded  by  an  exceedingly 
subtile  form  of  matter  called  the  ether,  and  light 
consists  of  waves  propagated  through  this  ether 
with  tremendous  rapidity.  The  average  number 
of  vibrations  in  a  second  is  estimated  to  be  over 
500,000,000,000,000,  and  they  travel  at  the  rate  of 
about  195,000  miles  per  second.  The  wave  theory 
of  light  is  only  a  theory,  and  the  existence  of  the 


SIGHT. 


255 


extremely  attenuated  form  of  matter  called  ether, 
which  can  neither  be  weighed,  seen,  heard,  nor  felt, 
but  only  postulated  from  certain  phenomena  sup- 
posed to  depend  upon  it,  is  only  inferred  ;  but  still 
this  theory  explains  almost  all  the  phenomena  of 
light,  and,  until  some  better  one  is  suggested,  must 
be  retained  as  a  working  hypothesis. 

From  these  facts,  we  can  judge  of  the  extraor- 
dinary delicacy  of  the  eye  as  an  organ  of  sense. 
Here  is  a  stimulus,  of  unknown  origin,  which  can 
traverse  the  widest  regions  of  space,  which  enables 
us  to  appreciate  the  existence  and  form  and  even 
the  structure  of  bodies  which  are  billions  of  miles 
away  from  us,  and  gives  us  more  knowledge  of  the 
external  world,  perhaps,  than  we  obtain  through  all 
our  other  senses  together,  and  yet  its  real  nature  is 
as  hidden  and  mysterious  and  impalpable  as  the  na- 
ture of  our  consciousness.  Let  us  now  examine  the 
structure  of  the  organ  which  perceives  this  strange 
stimulus  and  enables  it  to  affect  our  brain. 

317.  Situation  of  the  Eye. — The  eye  is  situated 
in  a  cavity  called  the  orbit,  surrounded  by  bone  ex- 
cepting in  front,  and  padded  all  about  with  fatty 
and  muscular  tissues,  so  that,  although  it  is  pro- 
tected from  injury  by  an  unyielding  bony  case,  it 
still  reposes  on  a  soft  and  elastic  bed. 

318.  Structure  of  the  Eyeball.  —  The  eyeball 
(Fig.  68)  is  nearly  spherical,  and  about  an  inch  in 
diameter.  It  is  formed  of  three  membranes,  ar- 
ranged concentrically  one  within  the  other,  and  the 
interior  is  filled  with  certain  structures  necessary  to 
vision.    The  outer  membrane  is  called  the  sclerotic* 

*  Sclcrot'iCy.  from  the  Greek  <TK\T)p6s,  hard,  because  it  is  the  hardest 
and  toughest  coat  of  the  eye. 


256 


ORGANS  OF  PERCEPTION. 


coat,  and  in  front,  where  it  is  visible,  constitutes 
what  is  commonly  known  as  the  white  of  the  eye. 


Fig.  68. — Horizontal  section  of  the  right  eye,  showing  the  relative  position 

of  its  parts. 

It  is  composed  of  white,  fibrous  tissue,  and  is  ex- 
ceedingly strong,  tough,  and  elastic.  It  surrounds 
the  whole  eyeball,  excepting  in  front,  where  a  trans- 
parent membrane,  about  ^th  of  an  inch  thick,  is  set 
into  it  like  a  watch-glass  in  the  case.  The  front  of 
the  eye  must  of  course  be  transparent  for  the  ad- 
mission of  light.  This  portion  of  the  eye  is  called 
the  cornea* 

*  Cornea,  from  the  Latin  cor'nu,  a  horn,  because  of  its  resemblance 
to  transparent  horn. 


SIGHT.  257 

Just  inside  the  sclerotic  coat  is  another  coat, 
called  the  cJioroid*  which  covers  the  whole  interior 
of  the  eye,  excepting  that  portion  bounded  by  the 
cornea.  This  coat  is  very  plentifully  supplied  with 
blood-vessels,  and  with  immense  numbers  of  minute 
cells,  filled  with  coloring-matter,  so  that  it  appears 
of  a  dark-brown  or  chocolate  color,  and  in  some 
persons  almost  black.  Inside  this  choroid  coat, 
again,  is  the  retina,\  which  is  an  exceedingly  deli- 
cate and  complicated  membrane  made  up  of  nerv- 
ous tissue,  and  upon  which  the  impressions  of  light 
are  received.  The  retina  is  spread  over  about  two 
thirds  of  the  inner  surface  of  the  eyeball,  not  reach- 
ing quite  as  far  forward  as  the  sclerotic  and  choroid 
coats. 

319.  The  Internal  Parts  of  the  Eye. — The  mem- 
branes above  mentioned  form,  so  to  speak,  the  in- 
casement  or  shell  of  the  eyeball.  The  bulk  of  the 
interior  of  the  eye  is  formed  by  the  vitreous  humor. % 
This  is  a  soft,  semi-fluid,  transparent,  jelly-like  body,* 

*  Choroid,  from  the  Greek  x^PL0V>  leather,  because,  being  dark-col- 
ored, it  resembles  leather  in  appearance. 

\  Ret'ina,  a  Latin  word,  meaning  in  that  language  just  what  it 
means  in  English.  It  is  derived  from  re'te,  a  net,  on  account  of  its 
mesh-like  appearance. 

\  Vit'reous,  from  the  Latin  vit'reus,  glassy. 

*  The  vitreous  humor  contains,  even  in  healthy  eyes,  minute  bodies, 
which  can  not  be  detected  from  the  outside,  but  which  can  be  seen, 
greatly  magnified,  by  the  person  himself.  They  are  called  "  musaz 
volitantes"  (literally ',  flitting  flies),  and  look  like  small  strings  of  bright 
beads,  or  little  transparent  spheres  or  fibers,  which  move  when  the  eye 
is  moved,  and,  when  the  eye  is  held  perfectly  still,  seem  to  sink  slowly. 
They  really  float  up  toward  the  top,  but  appear  to  go  down,  their  di- 
rection being  reversed  by  the  optical  apparatus  of  the  eye.  These  little 
objects  are  seen  most  vividly  against  a  bright  surface,  like  the  sky,  or  a 
white  wall,  and  when  perceived  for  the  first  time  are  apt  to  frighten 


258  ORGANS  OF  PERCEPTION. 

which  fills  the  ball  of  the  eye,  with  the  exception 
of  a  small  part,  about  one  sixth  of  the  mass,  in  front, 
which  contains  the  crystalline  lens  and  the  parts  be- 
tween the  lens  and  the  cornea.  This  vitreous  hu- 
mor is  surrounded  by  a  very  delicate  membrane, 
also  transparent,  which  lies  in  immediate  contact 
with  the  whole  extent  of  the  retina.  Just  where 
this  membrane  passes  in  front  of  the  vitreous  hu- 
mor, and  just  behind  the  cornea,  it  splits  in  two 
layers,  and  between  these  layers  is  suspended  and 
held  in  place  the  crystalline  lens.  This  lens  is  a 
double-convex  one,  with  the  posterior  curvature  a 
little  greater  than  the  anterior,  is  about  one  third  of 
an  inch  in  diameter  from  side  to  side  and  a  quarter 
of  an  inch  thick  at  its  middle.  It  is,  of  course,  per- 
fectly transparent,  and  acts  precisely  as  a  double- 
convex  lens  acts  in  any  optical  instrument.  Just  in 
front  of  the  lens  is  a  curtain,  with  a  hole  in  its  cen- 
ter, which  serves  to  regulate  the  admission  of  light 
to  the  interior  of  the  eye.  This  curtain  is  called 
the  i'ris*  and  it  contains  muscular  fibers,  to  which 
it  owes  its  power  of  contraction,  and  pigment-cells, 
to  which  it  owes  its  color,  varying  in  different  per- 
sons. The  hollow  space  between  the  cornea  in 
front  and  the  crystalline  lens  behind  is  filled  by  a 
fluid  called  the  aqueous  humorft  composed  almost 
entirely  of  water,  with  a  little  salt. 

320.  Uses  of  the  Two  Outer  Coats  of  the  Eye. 
— The  sclerotic  coat   serves,  by  its  toughness  and 

people.  They  exist,  however,  in  every  eye,  and  are  perfectly  harm- 
less. 

*TIpts,  a  Greek  word,  meaning  the  rainbow,  so  called  on  account  of 
the  variety  of  colors  it  presents  in  different  eyes. 

\  A ' queous,  from  the  Latin  a'queus,  watery,  because  it  consists  al- 
most entirely  of  water. 


SIGHT. 


259 


elasticity,  to  give  shape  to  the  organ,  and  protect 
the  parts  within.  The  cornea  in  front  answers  the 
same  purpose,  and  is  transparent,  in  order  to  allow 
the  passage  of  light.  The 
choroid  coat  serves  as  a 
nest  for  the  blood-ves- 
sels which  nourish  the 
retina,  and  also,  by  its 
dark  color,  prevents  the 
rays  of  light,  which  have 
once  passed  through  the 
retina,  from  passing  back 
again,  and  so  confusing 
the  sight.  When  the  light 
which  enters  the  eye  is 
so  intense  that  it  can  not 
be  absorbed  by  the  cho- 
roid, it  is  thus  reflected 
through  the  retina,  and 
our  sight  is  not  clear,  as 
we  have  a  double  im- 
pression, coming  from 
two  directions,  and  the 
ravs  conflict  with  each 
other.  We  call  this  "  be- 
ing dazzled."  In  albinos, 
the  coloring  -  matter  of 
the  choroid  is  absent, 
and  such  persons  always 
are  troubled  with  dimness  and  confusion  of  sight.* 


Fig.  69. — Vertical  section  of  the  ret- 
ina, highly  magnified.  At  the 
upper  part  of  the  cut  are  the  rods 
and  cones,  while  below  are  several 
distinct  layers  of  nerve-cells. 


*  Albinos  not  only  can  not  see  well,  because  they  are  dazzled  by 
the  light,  but  their  eyes  have  a  constant  vibratory  motion  from  side  to 
side,  like  the  pendulum  of  a  clock.  This  peculiar  affection  is  known 
to  physicians  as  nystagmus. 


26o  ORGANS  OF  PERCEPTION. 

321.  The  Retina. — The  retina  is  formed  by  the 
expansion  of  the  optic  nerve,  which  enters  the  eye 
behind  and  spreads  out  over  the  interior.  It  is  ex- 
ceedingly complicated  in  its  structure  (Fig.  69),  no 
less  than  eight  distinct  layers  being  found  in  its 
thickness,  although  the  whole  taken  together  is  very 
thin  and  delicate.  The  outermost  layer  is  made 
of  innumerable  minute  cylinders  of  nervous  matter 
of  different  shapes  and  sizes,  packed  together  side 
by  side  like  the  seeds  of  a  sunflower.  These  are 
called  the  rods  and  eoncs  of  the  retina.  Inside  of  these 
are  other  layers  of  tubes,  fibers,  cells,  and  granular 
matter,  all  of  which,  doubtless,  have  their  part  to 
play,  but  the  particular  function  of  which  is  not  yet 
known.  This  arrangement  of  the  nerve  substance  is 
necessary  to  the  sense  of  sight,  for,  singularly  enough, 
the  spot  where  the  optic  nerve  enters  the  eyeball  is 
entirely  blind.  This  nerve  can  convey  the  impres- 
sion of  sight  to  the  brain  as  it  receives  it  from  the 
special  sense-organ  the  retina ;  but,  if  light  falls  di- 
rectly upon  the  optic  nerve  itself,  no  sensation  is 
produced.  This  curious  and  interesting  fact  can  be 
easily  demonstrated. 

Make  a  round  black  spot  and  a  black  cross  upon 
a  white  card,  three  inches  apart  (Fig.  70).     Now 


+ 


Fig.  70. — Diagram  to  demonstrate  the  existence  of  the  blind  spot. 

hold  the  card  in  front,  at  a  distance  of  about  a  foot 
from  the  eyes,  close  the  left  eye,  and  look  at  the 
cross  with  the  right  one.     Both  the  cross  and  the 


SIGHT.  261 

black  spot  will  be  seen  distinctly.  Now  move  the 
card  slowly  toward  you,  still  keeping  the  right  eye 
fixed  upon  the  cross.  At  a  certain  point  the  round 
spot  will  disappear,  but,  as  the  card  continues  to 
approach  the  eye,  it  will  reappear  within  the  field 
of  vision.  At  the  point  of  disappearance,  its  image 
falls  upon  the  optic  nerve  just  where  it  enters  the 
eye  (Fig.  71).  Now,  if  this  blind  spot  were  just  in 
the  axis  of  the  eye,  we  should  be  badly  off,  for  it  is 

Circular  image  inside  the    Image  on  the  nerve        Image  outside  the 
nerve  (blind  spot).  (blind  spot).  nerve  (blind  spot). 


Fig.  71. — Diagram  illustrating  the  blind  spot.  It  represents  a  horizontal 
section  of  the  right  eye,  the  axis  of  the  eye  in  every  case  being  turned  to- 
ward the  cross. 

evident  that  we  should  be  unable  to  see  anything 
we  looked  directly  at.  But  the  point  of  entrance 
of  the  optic  nerve  is  toward  the  inner, side  of  the 
eyeball,  and  consequently  we  are  not  incommoded 
at  all  by  this  small  spot,  which  is  insensible  to  light. 

322,  Use  of  the  Crystalline  Lens, — The  interior 
of  the  eyeball  is,  therefore,  like  the  interior  of  a 
camera  obscara.  It  forms  a  dark  chamber,  lined  with 
a  dark  membrane,  to  absorb  superfluous  light,  and 
with  a  small  opening  in  front  to  admit  light.  Just 
behind  this  opening  is  the  lens. 

If  light  came  directly  into  the  eye,  and  fell  upon 
the  retina,  without  being  brought  to  a  focus,  our 
brains  would  appreciate  the  existence  of  the  light, 
but  would  not  get  clear  ideas  of  the  appearance  of 
objects.     Everything  would  be  dim  and  confused. 


262  ORGANS  OF  PERCEPTION. 

Something-  of  this  may  be  seen  in  a  camera  obscura, 
if  the  lens  be  removed.  The  rays  of  light,  as  they 
enter  the  camera,  still  form  an  image  of  outside  ob- 
jects, but  it  is  a  dull,  indistinct,  and  obscure  one. 
With  the  lens,  however,  the  picture  is  bright  and 
distinct  in  all  its  details.  The  reasons  for  this  are 
too  long  to  be  stated  here,  and  will  be  found  in  any 
treatise  on  optics.  Suffice  it  to  say  that  the  func- 
tion of  the  crystalline  lens  is  to  concentrate  the  rays 
of  light  as  they  enter  the  eye,  and  bring  them  to  a 
focus  on  the  retina. 

323.  The  Function  of  Accommodation.  —  The 
rays  of  light  being  affected  by  this  lens  precisely  as 
they  would  be  by  a  glass  one,  there  must  be  some 
provision  made  for  the  varying  distance  of  objects 
from  the  eye.  In  the  camera,  as  objects  are  nearer 
or  more  distant,  we  draw  out  or  push  in  the  lens, 
so  as  to  bring  it  farther  from  or  nearer  to  the  sur- 
face which  receives  the  image.  Now,  we  find  that, 
within  certain  limits,  a  healthy  eye  sees  objects  a 
moderate  distance  away  with  just  as  much  distinct- 
ness as  those  near  at  hand.  Moreover,  we  are  con- 
scious, as  we  change  rapidly  from  looking  at  a  dis- 
tant object  to  one  close  by,  of  a  kind  of  effort  in  the 
eye  itself.  There  must  be  a  change  of  some  kind 
there,  corresponding  to  the  pulling  out  or  pushing 
in  of  the  lens  of  the  camera.     What  is  the  change? 

There  is  a  short,  delicate  muscle,  called  the  cili- 
ary muscle,  one  extremity  of  which  is  attached  to 
the  stout  membrane  of  the  sclerotic  and  cornea  at 
their  junction,  and  the  other  extremity  to  the  cho- 
roid. The  muscle  is  a  circular  one,  reaching  all 
around  the  eyeball,  and  is  only  about  an  eighth  of 
an  inch  broad.     Now,  the  crystalline  lens  is  very 


SIGHT. 


263 


elastic,  and,  as  has  been  stated,  it  lies  between  two 
layers  of  a  membrane  which  passes  backward  and 
surrounds  the  vitreous  humor.  Under  ordinary 
circumstances,  these  two  layers  of  membrane,  one 
of  which  is  in  front  of  the  lens  and  the  other  be- 
hind it,  are  supposed  to  exercise  some  pressure  on 
it,  and  render  it  a  little  flatter  than  it  would  be,  if  it 
were  left  to  take  its  own  shape,  in  accordance  with 
its  elasticity.  Now,  suppose  that  we  wish  to  look 
at  an  object  close  at  hand.  The  ciliary  muscle  con- 
tracts and  the  membranes  surrounding  the  vitreous 
humor  are  drawn  forward  slightly.  As  a  conse- 
quence of  this  the  two  layers  of  membrane,  between 
which  the  lens  lies,  are  somewhat  relaxed,  and  exert 
less  pressure  on  the  front  and  back  of  the  lens.  The 
pressure  being  removed  from  it,  the 
elasticity  of  the  lens  makes  it  assume 
a  more  convex  shape  (Fig.  72),  and 
consequently  brings  the  rays  of  light 
to  their  proper  focus.  This  is  sup- 
posed to  be  the  method  by  which 
the  eye  accommodates  itself  to  differ- 
ent distances,  and  its  operation  is  so 
perfect  and  exact  that,  within  certain 
limits,  we  can  see  whatever  we  wish 
to.  Beyond  a  certain  distance,  and 
within  a  certain  distance,  this  accom- 
modation no  longer  occurs.  These 
distances  vary  with  different  per- 
sons, and  the  inner  limit  is  called  the  limit  of  dis- 
tinct vision. 

324.  The  Limit  of  Distinct  Vision. — The  limit  of 
distinct  vision  depends  on  the  accommodation  of 
the  lens  above  described.    As  any  object  is  brought 


Fig.  72. — Diagram 
showing-  how  the 
lens  changes  its 
form  for  near  and 
far  sight. 


264  ORGANS  OF  PERCEPTION. 

nearer  and  nearer  to  the  eye,  the  effort  required  to 
see  it  distinctly,  or,  in  other  words,  the  effort  at  ac- 
commodation, is  greater  and  greator,  until  at  length 
it  begins  to  be  accompanied  by  pain  and  a  peculiar 
sense  of  fatigue  in  the  eyes.  Within  this  point  dis- 
tinct vision  is  not  possible,  for  the  ciliary  muscle 
can  contract  no  further.  In  healthy  eyes,  this  limit 
is  usually  about  six  inches  from  the  cornea. 

As  objects  recede,  the  rays  from  them  come  to 
the  eye  at  a  smaller  and  smaller  angle,  until,  at 
the  distance  of  fifty  feet,  they  are  almost  parallel ; 
that  is,  they  are  practically  so,  as  far  as  the  percep- 
tion of  the  retina  is  concerned.  Beyond  this  point, 
vision  is  distinct  enough,  and  no  accommodation  of 
the  lens  is  required ;  but  a  new  difficulty  comes  in 
to  hamper  us  in  our  perception  of  objects.  We 
have  seen  that,  however  delicate  the  sense  of  touch 
may  be,  it  is  possible  to  press  two  points  of  a  com- 
pass on  the  skin  so  near  together  that  we  are  not 
able  by  the  sense  of  touch  to  say  whether  they  are 
two  points  or  one.  A  similar  condition  is  found  to 
exist  in  the  retina.  It  has  been  shown  by  experi- 
ment that,  if  two  objects  or  two  points  of  any  ob- 
ject are  so  near  together  that  both  combined  sub- 
tend an  angle  of  less  than  one  minute  at  the  lens, 
the  retina  can  not  distinguish  them  apart.  Beyond 
the  distance  of  fifty  feet,  then,  without  artificial  as- 
sistance, the  eye  is  unable  to  distinguish  objects 
perfectly  in  their  minute  details. 

325.  The  Function  of  the  Iris. — The  color  of 
the  iris  is  due  partly  to  the  blood-vessels  which  run 
through  it,  and  partly  to  small  pigment-cells.  In 
new-born  children  the  iris  is  always  blue,  and  does 
not  take  on  the  color  which  is  to  last  through  life 


SIGHT.  265 

for  several  weeks  after  birth.  The  iris  performs 
two  functions.  In  the  first  place,  in  every  lens,  the 
whole  of  which  is  made  of  the  same  substance  and 
of  the  same  density  throughout,  the  rays  of  light 
which  pass  through  and  near  the  center  are  not 
brought  to  a  focus  as  soon  as  those  which  pass 
through  near  the  circumference.  This  fact  causes 
a  blurring  of  the  image  (spherical  aberration)  and 
also  a  partial  decomposition  of  the  light  (chromatic 
aberration),  so  that  the  image  appears  colored  at 
its  edges.  In  optical  instruments  these  difficulties 
are  remedied,  partly  by  constructing  the  lens  of  two 
different  substances,  which  counteract  each  other's 
defects,  and  partly  by  covering  the  edge  of  the  lens 
and  only  allowing  the  light  to  come  through  the 
center  and  the  immediately  adjacent  parts.  The 
latter  method  is  the  one  carried  out  by  the  iris.  It 
is  pierced  in  the  center,  forming  the  pupil  of  the 
eye,  and  this  pupil  is  situated  immediately  in  front 
of  the  center  of  the  lens,  so  that  in  this  way  the 
faults  above  mentioned  are  corrected.  The  iris 
also  regulates  the  admission  of  light  to  the  eye. 
Too  much  light  irritates  the  retina,  and  by  reflex 
action  the  iris  contracts.  If  there  be  too  little  light 
the  iris  is  relaxed,  and  the  pupil  becomes  larger  so 
as  to  admit  more.  This  process  has  already  been 
mentioned  at  length. 

326.  The  Retina  and  Optic  Nerve  sensitive  only 
to  Light. — The  retina  is  sensitive  to  other  impulses 
than  that  of  light,  but,  whatever  these  impulses 
may  be,  the  sensation  of  light  is  the  only  one  con- 
veyed to  the  brain.  If  the  eyeball  be  struck  or 
pressed,  or  an  electrical  current  be  passed  through 
it,  we  see  sparks  or  flashes  of  light,  and  this  even 


266  ORGANS  OF  PERCEPTION. 

when  we  are  in  a  perfectly  dark  room.  This  is  due 
to  the  shock  to  the  retina,  from  which  every  stimu- 
lus of  whatever  kind  is  transmitted  by  the  optic 
nerve  to  the  brain  under  the  form  of  light. 

327.  Persistence  of  Impressions  on  the  Retina. 
— When  an  image  is  formed  on  the  retina,  espe- 
cially if  it  is  a  very  bright  one,  the  impression  re- 
mains a  little  while  after  the  object  that  caused  it 
has  passed  by.  The  consequence  of  this  is  that,  if 
several  objects  follow  each  other  in  very  rapid  suc- 
cession, new  images  are  continually  formed  on  the 
retina  before  those  that  immediately  preceded  them 
have  had  time  to  fade,  and  so  the  eye  does  not  de- 
tect any  interval  between  them.  Thus,  when  we 
look  at  a  swiftly-revolving  wheel,  we  do  not  see  the 
separate  spokes,  but  a  continuous,  hazy  blur;  and 
when  a  live  coal  is  whirled  around  fast  enough  be- 
fore the  eyes,  we  do  not  see  the  coal  in  its  proper 
shape,  but  only  a  luminous  circle.  In  this  tempo- 
rary persistence  of  impressions  on  the  sense  of 
sight,  it  is  like  all  the  other  senses. 

328.  Color-Blindness. — The  power  of  discrimi- 
nating between  different  colors  varies  very  much  in 
different  individuals.  While  some  can  not  only  dis- 
tinguish the  colors  with  ease,  but  can  pick  out  the 
most  delicate  shades  of  any  particular  color  with 
unfailing  accuracy,  others  are  unable  to  discrimi- 
nate, for  example,  between  red  and  green.  Such 
persons  are  called  color-blind,  and  can  not  see  any 
difference  between  the  fruit  and  the  leaves  of  a 
cherry-tree,  excepting  by  the  shape. 

329.  Near-Sight  and  Far-Sight. — In  the  natural 
and  healthy  eye  the  rays  of  light  are  brought  to 
a  focus  on  the  retina,  but  in  some  eyes  they  are 


SIGHT.  267 

not.  In  near-sighted  persons  the  eyeball  is  usually 
a  little  too  long,  and  the  rays  of  light,  being  brought 
to  a  focus  before  they  reach  the  retina,  cross  each 
other,  and  the  image  is  blurred.  In  far-sighted 
eyes  the  eyeball  is  too  short,  or  the  lens  is  too  flat, 
and  the  rays  are  not  brought  to  a  focus  at  all,  so 
that  the  effect  upon  vision  is  to  make  everything 
look  blurred,  as  in  the  former  case  (Fig.  73).  Both 
of  these  defects  can  and  should  be  corrected  by 
proper  glasses,  for  the  constant  straining  to  see,  of 


Fig.  73. — Diagram  showing  the  point  at  which  the  rays  of  light  are  brought 
to  a  focus  in  different  eyes. 

short-sighted  and  far-sighted  persons  who  try  to  get 
along  without  glasses,  eventually  injures  the  sight. 

330.  Muscles  of  the  Eyeball. — To  the  outside  of 
the  eyeball  are  attached  six  muscles,  by  means  of 
which  it  can  be  moved  in  any  direction.  Four  of 
them  pass  from  the  four  sides  of  the  eyeball  straight 
backward  to  the  bone  at  the  rear  of  the  orbit,  and 
move  the  eye  up  or  down,  and  to  the  right  or  left. 
The  other  muscles  are  attached,  one  to  the  upper 
and  the  other  to  the  lower  surface  of  the  eye-ball, 
their  other  ends  being  attached  to  the  bones  on  the 
inner  side  of  the  orbit  in  such  a  way  that,  by  their 
contraction,  the  eyeball  is  rolled  in  one  direction  or 
another. 


268  ORGANS  OF  PERCEPTION. 

331.  The  Eyelids  and  Eyebrows. — This  delicate 
organ — the  eye — is  protected  from  injury  in  front 
by  a  number  of  accessory  parts,  viz.,  the  eyelids,  eye- 
lashes, and  eyebrows. 

The  eyelids  are  composed  of  thin  pieces  of  car- 
tilage, covered  with  skin  on  the  outer  and  lined 
with  mucous  membrane  on  the  inner  side.  They 
are  movable,  and,  when  open,  expose  nearly  all  the 
iris  ;  when  shut,  they  completely  cover  the  eyeball. 
At  their  margins  are  several  short,  stiff  hairs — the 
eyelashes — which  project  outward  and  downward, 
and  serve  as  an  additional  protection  against  the 
entrance  of  dust  and  insects.  Above  the  eyes  are 
ridges  of  thick  skin,  also  covered  with  hairs,  and 
called  the  eyebrows,  which  turn  aside  the  perspira- 
tion or  other  fluids  which  run  down  the  forehead 
toward  the  eyes. 

332.  The  Tears. — In  order  to  keep  the  cornea 
perfectly  smooth  and  transparent,  and  to  preserve 
the  softness  of  the  mucous  membrane  lining  the  in- 
terior of  the  lids,  which  continually  sweep  over  the 
cornea,  and  if  rough  would  irritate  and  ruin  it,  a 
special  fluid  is  provided,  called  the  tears,  which  are 
continually  secreted,  and  keep  those  parts  constant- 
ly moist.  The  gland  which  provides  the  tears, 
called  the  lach'rymal gla7id  (¥'\g.  74),  is  situated  inside 
the  orbit,  just  above  and  outside  of  the  eyeball,  and 
its  secretion  is  poured  out  on  the  eye  by  several 
little  openings  at  the  upper  part  of  the  upper  lid, 
on  its  inner  surface.  By  the  winking  of  the  lids, 
which  occurs  frequently  and  is  usually  involuntary, 
it  is  spread  over  the  surface  of  the  eye.  On  the 
edge  of  the  lids,  near  the  inner  angle  of  the  eye, 
may  be  seen  two  minute  openings,  one  in  each  lid. 


SIGHT. 


269 


These  are  the  mouths  of  two  little  canals,  which 
pass  from  these  points  toward  the  nose,  soon  unit- 


FlG.  74. — Left  eyelids  from  behind.  Above  and  at  the  left  is  the  lachrymal 
gland.  On  the  lids  are  seen  what  look  like  strings  of  beads.  They  are 
glands  that  secrete  the  fatty  matter  that  coats  the  edges  of  the  lids,  and 
keeps  the  tears  from  running  over. 

ing  in  one  larger  canal,  which  runs  downward  into 
the  nasal  cavity.  Through  these  minute  canals,  the 
superfluous  tears  run  off  into  the  nose.  These 
canals  are  lined  with  mucous  membrane,  and,  dur- 
ing a  cold  in  the  head,  the  inflammation  often  closes 
them,  and  the  tears,  not  finding  free  passage  through 
them,  overflow  upon  the  cheeks.  This  overflow 
also  occurs  when  from  pain  or  any  powerful  emo- 
tion the  tears  are  increased  in  amount  so  that  the 
canals  are  unable  to  dispose  of  the  extra  supply. 
This  phenomenon  we  call  crying  or  weeping.  An 
overflow  of  tears  is  guarded  against  under  ordinary 
circumstances  by  an  oily  secretion  of  certain  glands 
in  the  lids,  which  is  discharged  just  along  their 
edges.  This  secretion  keeps  the  lids  from  sticking 
together  when  closed,  and  also  retains  the  tears,  un- 
less their  quantity  is  greater  than  common. 


270  ORGANS  OF  PERCEPTION. 

333.  Care  of  the  Eyes. — It  is  exceedingly  impor- 
tant that  proper  care  should  be  taken  of  the  eyes. 
They  arc  very  delicate,  and  yet  there  is  hardly  an 
organ  in  the  whole  body,  not  even  excepting  the 
stomach,  that  is  more  frequently  abused.  If  any- 
thing be  the  matter  with  the  eyes — if  they  smart,  or 
tingle,  or  itch,  or  the  sight  is  dim,  or  blurred,  or  in- 
distinct— a  good  oculist  should  immediately  be  con- 
sulted. More  is  known  about  the  eye,  probably, 
than  about  any  other  organ  in  the  body.  The  most 
eminent  scientists  in  the  world  have  spent  their  best 
years  in  the  study  of  it  in  health  and  disease,  and 
it  can  be  examined  inside  and  outside  thoroughly. 
As  a  consequence,  operators  who  devote  their  spe- 
cial attention  to  this  organ  generally  know  what 
they  are  about,  and  their  advice  should  be  carefully 
and  minutely  heeded.  It  will  not  do  for  individuals 
to  treat  their  own  eyes,  and  therefore  it  is  unneces- 
sary to  say  anything  about  its  disorders.  With  re- 
gard to  proper  care  of  the  eye,  it  is  almost  enough 
to  say,  Do  not  do  anything  to  produce  a  feeling  of 
"strain"  in  the  organ.  This  sensation,  as  already 
explained,  is  produced  by  the  effort  of  accommoda- 
tion, and,  as  the  muscular  contraction  accompany- 
ing this  act  compresses  the  interior  of  the  eye  some- 
what, it  causes  a  congestion  of  the  blood-vessels, 
which  is  usually  only  temporary,  and  passes  away 
when  the  cause  is  removed.  If  a  strain  like  this, 
however,  be  often  repeated  or  long  continued,  it  is 
apt  to  result  in  permanent  injury  to  the  sight,  just 
as  long-continued  congestion  of  the  blood-vessels  in 
any  other  part  of  the  body  will  impair  the  working 
of  the  organ  in  which  it  occurs.  The  same  effect  is 
produced   by   reading   or   using  the  eyes  for  fine 


SIGHT.  271 

work  while  stooping  or  lying,  or  during  the  inces- 
sant jarring  of  a  vehicle,  especially  a  railroad-car. 
The  eyes  should  not  be  rubbed,  or  pressed,  or 
squeezed,  or  used  by  a  bad  light,  or  in  any  other 
way  treated  as  if  they  could  bear  rough  usage.* 
They  can  not,  and,  if  they  are  abused,  the  sight  is 
apt  to  fail  in  a  sudden  and  alarming  manner. 

*  It  is  supposed  by  many  that  the  eyes  are  strengthened  by  being 
opened  in  cold  water  when  the  face  is  washed.  This  is  not  so.  On 
the  contrary,  it  is  an  exceedingly  injurious  practice,  and  frequently 
produces  little  ulcers  on  the  surface  of  the  eye,  which,  although  per- 
haps not  dangerous,  are  very  painful,  and  may  prevent  the  use  of  the 
affected  eye  for  several  days.  The  eyeball  is  washed  sufficiently  by 
the  tears. 


PART     VII. 

ORGAN  OF  SPEECH. 


334.  Structure  of  the  Larynx. — In  the  upper  part 
of  the  neck,  in  front,  is  a  hard,  projecting  mass, 
which,  in  the  throats  of  thin  persons,  is  plainly  vis- 
ible, and  in  every  one  can  be  easily  felt.  This  is 
commonly  called  Adams  apple,  and  consists  of  the 
projecting  cartilages  which  form  the  sides  of  the 
larynx.  This  organ  is  situated  at  the  upper  end  of 
the  trachea,  and  a  cross-section  of  it  is  nearly  trian- 
gular in  shape.  It  is  composed  mainly  of  cartilage, 
and  forms  a  stiff,  open,  box-like  organ,  covered  on 
the  outside  with  muscles,  and  on  the  inside  with 
mucous  membrane. 

335.  The  Vocal  Chords. — The  upper  end  of  the 
larynx  is  nearly  closed  by  muscular  and  membra- 
nous tissues,  which  divide  it  at  this  point  from  the 
throat.  But  it  has  a  chink-like  opening,  the  glottis, 
previously  described,  situated  at  the  base  of  the 
tongue,  just  behind  the  epiglottis.  This  is  the  es- 
sential organ  of  voice.  All  the  air  which  passes 
into  or  out  of  the  lungs  must  go  through  the  glot- 
tis.    Now,  in  front,  the  vocal  chords,  which  form  the 


ORGAN  OF  SPEECH.  273 

sides  of  the  glottis,  are  nearly  or  quite  in  contact, 
while  the  posterior  extremities  can  be  separated  to 
quite  a  distance  from  each  other.  These  posterior 
ends  are  attached  to  two  small  cartilages,  which  can 
be  rotated  by  certain  muscles,  so  as  to  separate  the 
vocal  chords.  When  certain  other  muscles  contract, 
which  act  in  an  opposite  direction,  the  cartilages  are 
rotated  inward,  and  the  vocal  chords  are  brought 
nearer  together.*  Other  muscles  render  the  chords 
tighter  or  looser,  according  to  circumstances  (Fig. 

75)- 

336.   How  the  Voice  is  produced. — Now,  when 

High  note.  Medium  note.  Low  note. 


Fig.  75. — The  vocal  chords  in  different  positions.     The  opening  between  the 

chords  is  the  glottis. 

the  air  is  forced  through  the  glottis  in  expiration 
with  sufficient  rapidity,  the  vocal  chords  are  thrown 
into  vibration,  and,  vibrations  being  thus  caused  in 
the  column  of  air  in  contact  with  them,  sound  is 
produced.  The  quality  of  this  sound,  as  well  as  its 
pitch  and  tone,  depends  upon  well-known  physical 
laws.  The  farther  apart  and  the  more  relaxed  the 
vocal  chords  are,  the  lower  will  be  the  sound  ;  the 

*  These  cartilages  are  triangular  in  shape,  and  act  very  much  like 
the  triangular  pieces  of  metal  to  which  bell-wires  are  fastened.  The 
vocal  chord  being  attached  to  one  corner,  and  the  muscle  to  another, 
while  it  rotates  about  the  third  angle,  it  is  evident  that  when  one  muscle 
contracts  the  vocal  chord  will  be  moved  outward,  and  when  another  op- 
posing muscle  contracts  the  end  of  the  chord  will  be  moved  inward. 


2/4 


ORGAN  OF  SPEECH. 


nearer  together  and  tighter  drawn  they  are,  the 
more  acute  will  be  the  sound.  Differences  also  de- 
pend upon  the  size  of  the  larynx  and  trachea,  the 
length  of  the  vocal  chords,  their  thickness  and 
smoothness,  the  condition  of  the  throat  and  parts 
adjacent,  etc. 

In  this  way  the  sound  is  made  which  we  call 
voice,  and  it  is  modulated  into  articulate  speech 
by  the  action,  separate  or  combined,  of  the  throat, 
nose,  palate,  tongue,  teeth,  and  lips.  To  consider 
how  these  variations  are  produced  would  require 
great  space,  and  be  foreign  to  the  purpose  of  this 
book.  It  is  sufficient  to  say  that  the  voice  is  pro- 
duced in  the  larynx,  and  articulation  performed  by 
the  parts  above  that  organ. 

337.  Abuse  of  the  Larynx. — Abuse  of  the  larynx 
produces  bad  results,  as  does  abuse  of  any  other  or- 
gan of  the  body.  Perhaps  the  most  common  form 
of  this  is  the  use  of  the  voice,  when  the  vocal  chords 
are  in  an  inflamed  or  congested  condition.  Over- 
use of  the  larynx  in  speaking  is  apt  in  many  persons 
to  bring  on  congestion  of  the  chords.  This  causes 
them  to  swell  a  little,  and  the  voice  loses  some  of 
its  clearness.  If  rest  be  not  given  the  organ  at 
such  a  time,  the  congestion  continues,  and  becomes 
chronic.  Then  the  voice  is  permanently  altered, 
becoming  rough  and  harsh  as  compared  with  its 
original  quality.  Very  often  a  sore-throat  extends 
to  the  glottis,  and  the  mucous  membrane  which 
covers  the  vocal  chords  becomes  inflamed.  Then 
the  usual  results  of  inflammation  of  a  mucous  mem- 
brane follow.  The  chords  swell  and  are  covered 
with  a  thick  secretion,  like  that  which  is  coughed 
up  during  such  an  attack.     This  thickening  of  the 


ORGAN  OF  SPEECH.  275 

chords  affects  the  voice,  and  makes  it  not  only 
harsh  but  of  a  lower  note  than  usual,  just  as  in  a 
violin  the  large  strings  give  forth  the  low  notes 
and  the  smaller  ones  the  high  notes.  The  secretion 
also  hinders  the  vibration  of  the  chords,  and  some- 
times the  voice  is  reduced  to  a  whisper  or  even  ex- 
tinguished, because  the  chords  are  so  disabled  as 
not  to  be  able  to  vibrate  at  all.  A  curious  phenom- 
enon sometimes  occurs  in  such  cases,  called  the 
"breaking  of  the  voice."  If  the  mucous  secretion 
be  very  viscid,  as  it  often  is,  the  chords  may  stick 
together  at  some  point  during  the  act  of  speaking, 
and  the  part  that  vibrates  is  instantly  reduced  in 
length  to  perhaps  three  quarters  of  what  it  was  a 
moment  before.  This  has  the  same  effect  as  the 
shortening  of  a  string  of  a  violin  by  pressing  it 
with  the  finger.  It  makes  the  voice  suddenly  take 
on  a  higher  note.  In  the  next  instant  the  chords 
become  entirely  separated,  and  the  former  note  re- 
turns, and  so  the  speech  consists  of  a  singular  series 
of  growls  and  squeaks. 

338.  Care  of  the  Larynx. — When  the  chords  are 
in  this  condition  they  ought  to  be  used  as  little  as 
possible,  or  permanent  injury  to  the  voice  will  be 
apt  to  result.  It  must  be  remembered  that  the  mu- 
cous membrane  of  the  larynx  in  such  cases  is  dis- 
eased and  sore,  and  ought  not  to  be  rasped  by  a 
forcible  current  of  air,  or  it  will  not  readily  recover. 
If  one  has  a  sore  spot  on  his  hand,  he  does  not  rub 
it  violently  several  times  a  day ;  he  lets  it  rest  until 
it  is  well  again.  In  such  a  case,  the  pain  which  re- 
sults from  rough  treatment  is  a  sufficient  indication 
of  its  harmfulness,  but  inflamed  or  congested  vocal 
chords  are  not  usually  painful,  and  the  use  of  the 


276  ORGAN  OF  SPEECH. 

voice  is  so  necessary  a  part  of  our  daily  life  that 
every  one  is  too  apt  to  neglect  warnings  regarding 
it.  But  Nature  is  inexorable,  and  shows  no  favor. 
Her  penalties  are  severe  and  unerring. 


QUESTIONS. 


PART   I. 


Chapter  I. — I.  What  is  anatomy  ?  Physiology?  Hygiene  ?  What 
is  an  anatomical  element  ?  A  tissue  ?  An  organ  ?  A  system  ?  An 
apparatus  ?  Give  examples  of  each.  What  is  the  function  of  an  or- 
gan? 

Chapter  II. — 2.  What  is  the  minute  structure  of  the  body  ?  Which 
is  the  original  element  ?  What  causes  the  different  consistency  of  dif- 
ferent organs  ?  3.  What  is  a  fiber  ?  Where  found  ?  4.  Why  is  the 
cell  so  important  ?  What  is  a  cell  ?  Nucleus  ?  Nucleolus  ?  5.  What 
is  protoplasm  ?  How  large  are  cells  ?  6.  What  other  kind  of  matter 
exists  in  the  body  ?  7.  What  is  the  difference  between  living  and  dead 
cells?  Illustration?  8.  How  do  cells  increase  in  number?  9.  What 
other  powers  do  cells  possess  ?  How  are  wounds  healed  ?  What  is 
said  of  "proud  flesh"  (foot-note)?  Does  one  cell  ever  perform  the 
duty  of  another  ?     Give  example  (foot-note). 

PART   II. 

Chapter  I. — 10.  Why  are  bones  necessary?  n.  How  does  living 
bone  differ  from  dead  bone  ?  12.  What  is  the  composition  of  bone  t 
What  experiments  will  show  this?  13.  How  are  bones  affected  by 
age  ?  What  is  a  "  green-stick  "  fracture  ?  14.  How  many  kinds  of 
bones  are  there  ?  What  is  the  structure  of  the  shaft  ?  Of  the  extrem- 
ities? Why  the  difference?  What  is  the  marrow?  15.  What  is  the 
periosteum?  What  is  the  minute  structure  of  bone  ?  16.  What  is  the 
use  of  the  periosteum  ?     Illustrate. 

Chapter  II. — 17.  How  many  bones  in  the  body  ?  What  is  ossifi- 
cation ?  When  complete  ?  18.  What  is  the  spine  ?  What  is  a  vertebra  ? 
How  are  the  vertebra?  arranged  in  the  spine  ?  What  separates  them  ? 
How  is  the  spinal  canal  formed,  and  what  does  it  contain  ?  19.  How 
13 


2;8  QUESTIONS. 

movable  is  the  spine?  How  is  it  held  together?  What  is  the  use  of 
the  pads  between  the  vertebra:  ?  Is  a  man  taller  in  the  morning  or  at 
night?  Why?  20.  What  is  the  skull  ?  How  are  its  bones  peculiar? 
What  is  the  advantage  of  its  arched  shape?  What  movable  bone  in 
the  skull?  21.  What  are  the  sutures  of  the  skull?  What  is  their 
u~-c?  22.  What  arc  the  frontal  sinuses?  How  may  they  cause  head- 
ache? 23.  Describe  the  ribs.  How  many  are  there?  How  are  they 
attached  to  the  breastbone  ?  What  are  the  floating  ribs?  How  does 
the  motion  of  the  ribs  alter  the  form  of  the  chest?  24.  How  do  the 
cartilages  of  the  ribs  change  with  age  ?  How  does  pressure  affect 
them?  What  is  the  natural  shape  of  the  chest?  25.  How  many  bones 
are  there  in  the  limbs  ?  What  is  meant  by  homologous  bones  ?  26. 
How  are  joints  formed  ?  What  is  cartilage?  Synovial  membrane? 
Ligaments  ?     Uses  of  these  parts. 

Chapter  III. — 27.  What  is  a  fracture?  A  dislocation  ?  How  can 
they  be  told  apart  ?  28.  How  are  bones  generally  broken,  and  why 
does  the  limb  generally  become  shorter  after  a  fracture  ?  Why  is  a 
fracture  near  a  joint  so  serious  ?  29.  W'hy  is  a  dislocation  so  painful  ? 
In  what  joints  are  dislocations  most  common  ?  How  are  they  generally 
caused  ?  What  is  a  sprain  (foot-note)  ?  30.  How  long  does  it  take  a 
broken  bone  to  unite?  31.  How  should  a  broken  limb  be  cared  for 
before  the  doctor  comes  ?     How  can  the  patient  be  carried  ? 

Chapter  IV. — 32.  How  are  the  bones  moved?  What  two  kinds 
of  muscle  are  there?  33.  What  is  a  voluntary  muscle  ?  What  is  con- 
nective tissue  (foot-note)?  Use  of  muscle.  How  does  voluntary  mus- 
cular fiber  look  under  the  microscope?  What  is  striation  ?  34.  What 
is  the  minute  structure  of  involuntary  muscular  fiber?  35.  How  do 
voluntary  and  involuntary  muscles  differ  in  their  action  ?  Peculiarity 
of  the  heart-muscle.  Where  are  involuntary  muscles  found  ?  36.  Do 
muscles  vary  much  in  size  ?  Illustrate.  37.  How  are  the  muscles  con- 
nected with  the  bones  ?  WTiat  is  a  tendon  ?  Describe  the  peculiar 
arrangement  of  tendons  at  the  wrist  and  ankle.  38.  Describe  the  dis- 
advantages under  which  a  muscle  exerts  its  force  during  contraction. 
39.  What  is  the  irritability  of  muscle  ?  Give  illustrations.  40.  W hat 
is  meant  by  the  muscular  sense  ?  Of  what  use  is  this  sense  ?  41.  Illus- 
trate the  use  of  this  sense  in  standing.  42.  What  is  the  effect  of  con- 
traction on  the  muscle  itself  ?  43.  What  is  the  effect  of  muscular  over- 
work ?  44.  Wrhat  is  the  result  of  muscular  inactivity  ?  Give  illustra- 
tions. How  is  curvature  of  the  spine  produced  (foot-note)?  45.  What 
is  the  best  exercise  ?  What  is  said  of  gymnastic  training  ?  46.  Why  is 
exhaustion  dangerous  ?  47.  Why  is  rest  necessary  ?  What  simple  rules 
for  exercise  are  given  ? 


QUESTIONS.  279 


PART    III. 

Chapter  I. — 48.  Why  do  we  need  food  ?  49  Can  people  live 
without  eating  ?  Why  ?  50.  What  are  the  two  great  divisions  of  foods  ? 
51.  What  proportion  of  the  body  is  water?  How  much  water  is  need- 
ed daily  ?  52.  Illustrate  the  importance  of  salt  (foot-note).  53.  What 
other  inorganic  substances  are  taken  in  food  ?  Why  is  lime  so  impor- 
tant? 54.  What  are  the  non-nitrogenous  foods?  55.  In  what  foods  is 
starch  found?  What  peculiarity  has  starch?  56.  In  what  foods  is 
sugar  found  ?  Name  some  of  the  varieties  of  sugar.  What  is  said  of 
glucose  (foot-note)?  57.  What  is  the  use  of  fat  in  the  body?  Is  the 
fat  all  taken  into  the  body  with  the  food?  What  articles  of  food  tend 
to  produce  fat  ?  Illustrate.  Describe  Mr.  Banting's  case  (foot-note). 
58.  What  are  nitrogenous  foods?  What  other  name  are  they  known 
by  to  physiologists  ?  In  what  foods  are  the  nitrogenous  substances 
found?  Are  similar  substances  found  in  vegetable  foods?  59.  Why 
do  we  need  variety  in  our  food  ?  60.  Which  is  the  most  essential  of  all 
articles  of  food  or  drink?  Illustrate.  61.  How  much  of  each  kind  of 
food  is  needed  daily  ?     62.  What  is  the  effect  of  cooking  on  food  ? 

Chapter  II. — 63.  What  is  the  use  of  the  digestive  apparatus? 
64.  What  are  the  five  stages  in  the  preparation  of  food  for  the  needs  of 
the  body  ?  65.  Which  of  these  stages  is  under  control  of  the  will? 
Why  must  all  the  stages  be  properly  carried  through?  66.  Use  of  the 
senses  of  taste  and  smell.  67.  Use  of  the  teeth.  Of  the  cheeks  and 
tongue.  What  is  the  masseter  muscle?  What  is  said  of  the  sound 
accompanying  muscular  contraction  ?  68.  What  is  the  saliva  ?  What 
are  the  parotid  glands  ?  How  does  their  secretion  differ  from  that  of 
the  other  salivary  glands  ?  Does  the  secretion  of  saliva  vary  in  amount 
at  different  times  ?  Illustrate  (foot-note).  69.  What  are  the  properties 
of  the  saliva  ?  Its  effect  upon  starch  ?  Its  use  in  the  preparation  of 
food.  Illustrate.  How  much  saliva  is  secreted  daily  ?  What  is  said 
of  the  care  of  the  teeth  (note)  ? 

Chapter  III. — 70.  What  is  the  alimentary  canal?  71.  What  is 
mucous  membrane  ?  Its  minute  structure  ?  What  are  epithelial  and 
epidermal  cells  (foot-note)  ?  72.  Describe  the  character  and  arrange- 
ment of  the  muscles  in  the  alimentary  canal.  What  is  the  result  of 
their  contraction  ?  73.  What  is  serous  membrane  ?  Its  use  ?  74. 
What  are  the  pharynx  and  oesophagus?  How  do  we  swallow  ?  75. 
How  large  is  the  stomach  ?  What  is  its  shape  ?  Where  are  its  two 
openings,  and  what  are  they  called  ?  What  is  the  great  pouch  of  the 
stomach  ?  In  what  direction  do  substances  pass  through  the  stomach, 
and  how  is  this  regulated  ?     76.  What  portions  of  the  food  are  digested 


28o  QUESTIONS. 

in  the  stomach?  77.  Describe  the  accident  to  St.  Martin,  and  its  re- 
sult. 7S.  What  is  the  appearance  of  the  interior  of  a  healthy  stomach? 
79.  How  does  the  gastric  juice  appear  during  secretion?  When  is  it 
secreted?  80.  What  two  necessary  ingredients  has  the  gastric  juice  ? 
Can  food  be  digested  outside  of  the  body?  How  much  gastric  juice  is 
secreted  daily  ?  81.  What  part  do  the  muscles  of  the  stomach  perform 
during  digestion?  82.  What  is  the  appearance  of  the  interior  of  the 
stomach  during  indigestion?  Is  the  gastric  juice  secreted  at  such 
times?  How  is  the  tongue  affected?  83.  How  long  a  time  is  re- 
quired for  stomach-digestion?  84.  How  does  thorough  mastication 
assist  digestion,  and  why?  85.  What  is  said  of  eating  too  little?  86. 
Why  is  it  harmful  to  eat  too  much  ?  87.  Why  should  we  not  eat  be- 
tween meals?  88.  What  is  hunger?  Why  is  plain  food  the  best? 
89.  How  are  we  to  know  when  we  have  eaten  enough?  How  far 
apart  should  our  meals  be?  90.  How  are  we  to  judge  of  what  to  eat  ? 
91.  What  is  said  of  pepper  and  mustard?  What  is  the  golden  rule 
about  eating?  92.  What  is  the  natural  drink  ?  93.  What  are  the  im- 
mediate effects  of  drinks  containing  alcohol  ?  94.  What  is  the  pecul- 
iarity of  narcotic  poisons?  95.  What  is  the  earliest  symptom  of  nar- 
cotic poisoning  ?  96.  W7hat  is  the  effect  of  alcohol  on  growing  persons  ? 
97.  What  are  the  effects  of  habitual  excess  in  the  use  of  alcoholic 
drinks?  98.  What  effect  has  alcohol  upon  the  powers  of  endurance? 
Does  it  enable  men  to  bear  heat  and  cold  better?  Why  does  it  seem 
to  ?  Does  it  ward  off  disease  ?  99.  What  effects  have  tea  and  coffee 
on  growing  persons?  Also  tobacco  (foot-note)?  100.  How  is  candy 
adulterated?  What  kinds  are  to  be  avoided?  Why?  101.  What  is 
the  trichina  spiralis  ?  The  cysticercus  cellulosce  ?  How  can  they  be 
killed  ?     What  are  the  general  rules  about  eating  ? 

Chapter  IV. — 102.  What  becomes  of  the  fats,  sugars,  and  starches 
in  the  stomach?  What  is  the  chyme?  103.  What  is  the  structure  of 
the  small  intestine?  How  does  it  join  the  large  intestine?  What  is 
the  course  of  the  latter  ?  What  is  the  appendix  vermiformis  (foot-note)  ? 
104.  How  do  the  muscular  fibers  of  the  intestine  contract  ?  What  is 
the  result?  105.  What  is  the  duodenum?  106.  What  is  the  pan- 
creas? What  is  its  use?  107.  What  is  the  liver?  Its  secretion? 
108.  What  other  function  has  the  liver?  109.  What  is  the  bile? 
Where  is  it  discharged  into  the  intestine  ?  What  reason  is  there  for 
supposing  that  it  is  an  excrementitious  fluid?  What  is  jaundice? 
What  is  the  result  if  the  bile  is  prevented  from  entering  the  intestine  ? 
Illustrate.  Does  the  bile  leave  the  body  ?  What  is  the  inference  from 
these  facts?  no.  What  are  the  intestinal  juices  ?  How  are  they  use- 
ful ?     in.  How  is  it  shown  that  food  is  absorbed  from  the  intestine? 


QUESTIONS.  28l 

What  vessels  absorb  it  ?  Origin  of  the  name  lacteal  (foot-note)  ?  112. 
What  is  the  peritonaeum  ?  Its  use  ?  How  do  the  blood-vessels  and 
lacteals  get  to  the  intestine  ?  Where  do  they  terminate  ?  113.  What 
are  the  villi  ?  Their  size,  number,  and  structure  ?  114.  What  are  the 
lymphatics  ?  The  lymph  ?  The  lymphatic  glands  ?  What  is  the 
function  of  the  lymphatics?  What  are  the  lacteals?  The  thoracic 
duct?  115.  Where  is  the  blood  from  the  intestines  carried?  116. 
What  is  the  function  of  the  villi  ?  What  is  the  chyle  ?  How  is  it 
absorbed  (foot-note)?  117.  Describe  the  changes  in  the  blood  during 
digestion.  118.  What  is  the  spleen?  Why  would  it  seem  to  be  an 
important  organ  ?  What  is  the  result  of  its  removal  ?  What  is  prob- 
ably its  function  (foot-note)  ? 

Chapter  V. — 119.  What  is  the  blood?  Its  physical  properties? 
120.  What  are  the  red  blood-corpuscles  ?  Their  appearance  and  size  ? 
How  do  they  differ  in  different  animals?  121.  What  are  the  white 
blood-corpuscles  ?  How  numerous  are  they  ?  What  is  their  appear- 
ance and  size  ?  How  much  of  the  blood  is  made  up  of  corpuscles  ? 
122.  What  is  the  plasma?  Its  composition  ?  123.  What  is  coagula- 
tion ?  What  is  the  clot  ?  The  serum  ?  Why  is  the  clot  red  ?  How 
does  serum  differ  from  plasma?  124.  What  conditions  affect  the 
rapidity  of  coagulation  ?  Will  blood  coagulate  inside  of  the  body  ? 
Illustrate.  125.  What  is  the  total  amount  of  blood  in  the  human 
body?  126.  What  gas  is  absorbed  by  the  blood  from  the  air?  How 
important  is  it  to  life  ?  Illustrate.  127.  What  process  causes  the  blood 
to  change  color? 

Chapter  VI. — 128.  Is  respiration  a  simple  process?  129.  What 
is  the  structure  of  the  interior  of  the  nose  ?  Why  is  it  better  to  breathe 
through  the  nose  than  through  the  mouth  ?  130.  What  is  the  trachea  ? 
What  are  the  bronchi?  How  are  these  tubes  kept  open?  Do  the 
rings  of  the  trachea  entirely  surround  it  ?  Why  not  ?  What  is  the 
larynx?  What  is  the  glottis?  Where  is  it  situated?  131.  What  are 
the  vocal  chords  ?  What  is  the  epiglottis?  Its  use?  132.  What  are 
the  lungs,  their  situation,  appearance,  and  weight?  133.  What  is  the 
minute  structure  of  the  lungs  ?  What  is  a  pulmonary  lobule  ?  A  pul- 
monary vesicle  ?  Their  size  ?  134.  What  peculiarity  has  the  lining 
membrane  of  the  lungs?  What  is  the  function  of  the  cilia?  135. 
What  is  asthma  ?  136.  Where  are  the  blood-vessels  of  the  lungs 
situated?  137.  What  is  the  pleura?  Its  use?  What  is  pleurisy? 
138.  How  is  inspiration  effected?  What  are  the  situation  and  use  of 
the  diaphragm  ?  What  is  hiccough  (foot-note)  ?  139.  How  is  expira- 
tion effected  ?  140.  Which  is  the  more  powerful  action,  inspiration  or 
expiration  ?     141.  How  much  air  is  taken  into  the  lungs  with  each  in- 


282  QUESTIONS. 

spiration?  What  is  the  entire  capacity  of  the  lungs?  How  much  air 
can  be  expelled  with  a  forcible  expiration  ?  142.  What  is  meant  by 
the  diffusion  of  gases?  What  is  the  function  of  the  cilia?  How  is 
the  air  in  the  lungs  changed  otherwise  than  by  respiration?  143.  How 
much  air  is  respired  daily?  How  would  you  calculate  the  amount ? 
144.  What  is  the  composition  of  air  as  it  enters  the  lungs?  How  is  it 
changed  there?  How  much  water  is  expired  daily?  145.  How  much 
oxygen  disappears  in  the  body?  How  was  the  carbon  dioxide  for- 
merly supposed  to  be  formed  ?  How  can  this  theory  be  disproved  ?  146. 
What  gives  the  breath  its  peculiar  odor?  147.  How  is  the  blood  changed 
in  the  lungs?     What  is  the  cause  of  the  change  in  color  (foot-note)? 

148.  Where  is  the  carbon  dioxide  found  ?     How  much  is  expired  daily  ? 

149.  How  is  the  air  changed  by  respiration  ?  Importance  of  moisture 
in  the  air  (foot-note).  150.  Effect  of  plants  on  the  composition  of  the 
air.  151.  How  does  the  air  of  houses  become  unfit  to  breathe?  What 
is  the  effect  of  combustion?  What  is  the  most  dangerous  impurity 
added  to  the  air  by  the  breath?  152.  What  is  ventilation?  How  can 
it  be  effected  ?  What  becomes  of  the  organic  matter  of  the  breath  in 
the  open  air?  153.  What  are  contagious  diseases?  How  are  they 
communicated  from  one  person  to  another  ?  Malarial  fevers,  sewer- 
air  (foot-notes).  154.  How  are  these  diseases  prevented  from  spread- 
ing?    What  precautions  are  to  be  taken  in  the  sick-room?    And  why? 

Chapter  VII. — 155.  What  is  asphyxia?  How  produced?  How 
is  the  color  of  the  surface  of  the  body  affected  by  it?  156.  How  long 
may  a  person  remain  under  water  without  dying?  157.  What  should 
be  done  to  resuscitate  a  person  who  has  been  under  water  until  he  is 
unconscious?  And  why?  158.  WThat  is  the  object  of  artificial  respi- 
ration? Describe  the  method  of  performing  it.  What  is  the  first  sign 
of  recovery?  159.  What  precautions  are  necessary  with  regard  to  the 
throat  and  tongue  ?  What  should  be  done  when  the  person  begins  to 
breathe  ?     Importance  of  fresh  air  (foot-note). 

Chapter  VIII. — 160.  How  is  the  circulation  of  the  blood  effected? 

161.  What  is  the  heart?     Its  situation?     What  is  the  pericardium? 

162.  Describe  the  double  circulation.  163.  Describe  the  course  of  the 
blood  in  the  two  sides  of  the  heart.  Why  does  the  blood  always  go 
forward  and  never  backward  ?  164.  How  is  each  side  of  the  heart 
divided?  How  many  cavities  are  there  altogether?  What  are  they 
called?  What  is  the  course  of  the  blood  through  them?  165.  How 
many  sets  of  valves  has  the  heart?  Where  are  they  situated?  What 
is  their  use?  166.  What  large  blood-vessels  are  connected  with  the 
heart?  167.  Describe  the  circulation  of  the  blood  more  fully.  168. 
What  peculiarity  in  the  arrangement  of  certain  valves  in  the  heart  ? 


QUESTIONS.  283 

And  what  is  the  effect  of  this  peculiarity  ?  169.  How  does  the  heart 
contract  and  relax  ?  170.  What  are  the  sounds  of  the  heart?  How 
are  they  produced?  171.  How  frequently  does  the  heart  contract? 
How  may  the  rapidity  of  contraction  vary,  and  what  conditions  affect 
it  ?  Can  its  contractions  ever  be  controlled  by  the  will  ?  Give  illus- 
tration. 

Chapter  IX. — 172.  How  is  the  work  of  the  heart  assisted?  173. 
What  is  the  structure  of  the  arteries  ?  How  many  layers  ?  What  is 
the  use  of  the  elastic  fibers?  174.  How  is  the  pulse  produced?  Where 
can  it  be  felt  ?  175.  How  do  the  arteries  divide  into  branches,  and  how 
do  their  walls  change  as  they  become  smaller  ?  176.  What  are  the 
capillaries?  How  large  are  they?  How  numerous?  Illustrate.  177. 
What  is  the  structure  of  the  veins  ?  What  is  the  result  of  their  struct- 
ure ?  What  are  the  vena?  cavae?  178.  What  effect  has  respiration  on 
the  flow  of  blood  in  the  veins  ?  And  how  ?  179.  What  effect  has  mus- 
cular contraction?  And  how?  180.  What  is  the  use  of  the  valves  in 
the  veins?  How  can  this  be  illustrated  ?  181.  How  do  the  capillaries 
assist  the  venous  flow?  182.  What  is  said  of  communicating  blood- 
vessels? 183.  Give  a  brief  review  of  the  course  of  the  circulation. 
How  rapidly  does  the  blood  flow  in  the  arteries  ?  How  rapidly  in  the 
capillaries?  Describe  the  circulation  as  seen  in  the  frog's  foot.  184. 
What  artery  carries  black  blood,  and  what  vein  scarlet  blood  ?  And 
why?  185.  How  rapidly  does  the  blood  flow  in  the  veins?  Why  is 
not  the  rapidity  of  the  blood-current  the  same  in  arteries  and  veins  ? 
186.  How  rapid  is  the  general  circulation?  What  experiment  has 
been  made  to  determine  this  ?  How  long  does  it  take  for  all  of  the 
blood  to  pass  through  the  heart  ?  How  is  this  calculated  ?  187.  What 
are  the  vaso-motor  nerves?  How  do  they  affect  the  circulation  ?  188. 
What  is  the  aorta?  What  is  its  course?  189.  What  are  the  femoral 
arteries?  Their  course  ?  190.  What  are  the  brachial  arteries?  Their 
course?  The  radial  and  ulnar  arteries?  191.  What  arteries  supply 
the  head  and  face?  What  is  the  course  of  the  carotid  arteries?  192. 
Where  are  the  veins  usually  situated  ?  What  are  the  jugular  veins  ? 
What  other  large  and  important  veins  are  there  ?  How  many  pulmo- 
nary arteries  ?     How  many  pulmonary  veins? 

Chapter  X. — 193.  WThat  happens  when  the  circulation  of  blood  in 
any  part  of  the  body  is  obstructed  ?  Illustrate.  How  is  the  swelling 
caused?  What  is  dropsy?  What  happens  when  the  obstruction  is  re- 
moved? 194.  What  is  the  result  of  disease  of  the  valves  of  the  heart  ? 
How  is  shortness  of  breath  produced  ?  How  is  general  dropsy  pro- 
duced by  such  disease  ?  What  is  the  result  of  disease  of  the  aortic 
valves  ?     What   may  result   from   inflammation  of  the   edges  of  the 


284  QUESTIONS. 

valves?  How  may  gangrene  be  caused?  195.  How  do  physicians 
detect  heart-disease  ?  196.  Effect  of  coagulation  on  bleeding.  197. 
What  are  some  of  the  conditions  of  coagulation  ?  Illustrate.  198. 
How  can  the  bleeding  from  an  artery  be  distinguished  from  that  from 
a  vein  ?  199.  How  does  Nature  stop  haemorrhage?  200.  How  does 
cold  arrest  bleeding?  201.  What  are  styptics?  Name  some  of  them. 
What  is  their  effect  on  the  blood  ?  What  is  the  objection  to  their  use? 
202.  How  is  compression  applied  to  a  wound  ?  Where  should  an  ar- 
tery be  compressed  ?  And  a  vein  ?  203.  How  does  Nature  arrest 
bleeding  permanently?  How  do  surgeons  assist  the  process?  What 
is  the  use  of  ligatures  ?  204.  State  briefly  the  means  of  arresting 
hemorrhage.  205.  How  is  bleeding  from  wounds  of  the  limbs  to  be 
stopped?  How  is  the  knotted  handkerchief  to  be  used?  206.  What 
is  the  cause  of  fainting,  and  what  is  to  be  done  for  it  ?  207.  What 
does  shortness  of  breath  always  indicate  ?   Why  does  exercise  cause  it? 

PART    IV. 

Chapter  I. — 208.  What  is  said  of  the  difficulty  of  investigating 
the  nervous  system?  209.  What  are  the  two  great  divisions  of  the 
nervous  system  ?  What  are  they  called  ?  What  are  their  functions  ? 
210.  What  are  the  two  forms  of  nervous  tissue  ?  211.  What  is  the 
structure  of  the  white  substance?  How  large  are  nerve-fibers?  What 
is  the  myelin  ?  The  axis-cylinder  ?  Wrhat  are  supposed  to  be  the  func- 
tions of  these  different  parts  of  the  nerve-fiber?  212.  What  does  the 
gray  substance  consist  of?  How  large  are  nerve-cells?  WThat  is  their 
structure  ?  What  relation  is  supposed  to  exist  between  the  cells  and 
the  fibers  ?  W7hat  is  the  function  of  the  fibers  ?  What  of  the  cells  ? 
213.  Wliat  is  the  structure  of  a  nerve?  How  do  its  constituent  parts 
vary  in  different  situations?  What  kind  of  nervous  substance  is  most 
abundant?  214.  What  are  nervous  ganglia  ?  215.  Illustrate  the  func- 
tions of  sensation  and  motion  as  exhibited  by  nerves.  What  is  reflex 
action?  WThy  so  called?  216.  What  is  said  of  the  rapidity  of  the 
nervous  force?  Give  an  illustration.  217.  Do  nerves  become  ex- 
hausted? How?  218.  How  can  it  be  shown  that  nerves  are  mere 
conductors  of  force?  219.  What  are  the  reasons  for  believing  that  the 
gray  substance  originates  force  ?  How  does  the  nerve-force  differ  from 
electricity  ?  220.  What  part  of  the  nervous  system  supplies  the  volun- 
tary muscles  with  nerves?  And  what  part  the  involuntary  ones  ?  W7hat 
part  is  under  our  own  control  ? 

Chapter  II. — 221.  What  is  the  structure  of  the  sympathetic  sys- 
tem?    How  large  are  the  ganglia?     Where  are  they  situated?     What 


QUESTIONS.  285 

is  said  about  the  solar  plexus  (foot-note)?  222.  What  is  said  of  the 
rapidity  of  action  of  the  sympathetic  system?  How  is  it  illustrated  in 
disease?  223.  How  is  it  illustrated  by  the  pupil  of  the  eye?  224. 
What  is  the  effect  of  dividing  a  sympathetic  nerve  ?  How  may  it  be 
shown  on  the  ear  of  a  rabbit?  What  do  these  facts  indicate?  225.  If 
the  sympathetic  nerve  supplying  a  gland  is  divided,  what  effect  is  pro- 
duced? How  is  "watering  of  the  mouth"  caused?  226.  How  is 
blushing  produced?  Why  is  it  more  evident  in  the  cheeks?  What 
facts  show  that  it  is  regulated  by  the  sympathetic  nerves  ?  How  can 
the  blush  be  prevented?  227.  What  are  the  vaso-motor  nerves?  Why 
so  called?  Are  the  cerebro-spinal  and  sympathetic  systems  entirely 
distinct  from  each  other  ?  228.  What  system  regulates  the  process  of 
digestion  ?  How  may  this  process  be  affected  by  the  emotions?  229. 
What  effect  has  cold  on  the  sympathetic  nerves  ?  How  may  serious 
disease  be  brought  on  by  exposure?  How  do  persons  catch  cold,  and 
how  may  colds  be  prevented  (foot-note)?  230.  What  are  the  signs  of 
exhaustion  of  the  sympathetic  system  ?     How  is  it  to  be  relieved  ? 

Chapter  III. — 231.  Describe  the  spinal  cord.  How  are  the  gray 
substance  and  the  white  substance  arranged  respectively  ?  What  are 
the  fissures  of  the  cord?  232.  How  many  pairs  of  spinal  nerves  are 
there?  What  parts  of  the  body  do  they  supply  ?  233.  What  are  the 
properties  of  the  spinal  nerves  ?  234.  What  two  kinds  of  sensibility 
exist  in  these  nerves?  How  is  this  shown  ?  235.  What  is  the  effect  of 
dividing  a  spinal  nerve  ?  How  can  sensation  and  motion  both  be  con- 
veyed by  the  same  nerve  ?  236.  How  many  roots  has  a  spinal  nerve  ? 
How  does  the  posterior  root  differ  in  appearance  from  the  anterior  ? 
How  are  the  spinal  nerves  formed,  and  how  do  they  divide  ?  237.  What 
effect  is  produced  by  dividing  the  anterior  root  of  a  spinal  nerve  ?  What 
does  this  experiment  prove  ?  23S.  What  effect  is  produced  by  dividing 
the  posterior  root  of  a  spinal  nerve  ?  What  does  this  experiment  prove  ? 
239.  What  do  these  experiments  show  with  regard  to  the  structure  of 
spinal  nerves  ?  240.  How  is  the  spinal  cord  connected  with  the  brain  ? 
What  is  said  of  the  crossing  of  fibers  from  one  side  to  the  other  ?  241. 
Why  are  sensations  always  referred  to  the  extremity  of  the  nerve? 
Give  illustrations.  242.  What  is  the  use  of  the  gray  matter  in  the 
center  of  the  spinal  cord  ?  Describe  the  experiment  with  the  frog. 
What  does  it  show?  243.  How  does  Nature  perform  similar  experi- 
ments for  us  upon  men?  Illustrate.  244.  What  are  automatic  ac- 
tions?   Illustrate. 

Chapter  IV. — 245.  What  is  the  distinction  between  the  brain  and 
the  cerebrum?  What  is  said  of  the  removal  of  the  cerebrum?  246. 
What  is  the  structure   of  the  cerebrum  ?     What  are  the  convolutions  ? 


286  QUESTIONS. 

How  is  the  gray  matter  distributed?  Is  the  cerebrum  sensitive  to  in- 
jury? 247.  What  is  the  function  of  the  cerebrum?  248.  Does  intel- 
ligence seem  to  increase  with  the  size  of  the  brain  ?  Illustrate.  What 
is  the  weight  of  the  human  brain  ?  249.  How  much  do  human  brains 
differ  in  weight?  Illustrate.  How  would  you  account  for  a  small 
brain  in  a  clever  man  ?  250.  What  effect  do  injuries  of  the  brain  have 
upon  the  mind  ?  251.  What  is  the  effect  of  removal  of  the  cerebrum 
of  a  pigeon  ?  252.  What  is  the  effect  of  softening  of  the  cerebrum  in 
man  ?  253.  State  briefly  the  evidence  that  the  cerebrum  is  the  seat  of 
intelligence.  254.  What  is  the  structure  of  the  cerebellum?  Its  size? 
255.  What  is  the  effect  of  removal  of  the  cerebellum  of  a  pigeon? 
What  does  this  experiment  seem  to  show?  What  is  the  effect  of  dis- 
ease of  this  organ  in  man?  What  is  inferred  from  these  facts  as  to 
the  function  of  the  cerebellum?  256.  What  is  the  function  of  the 
tubercula  quadrigemina  ?  How  can  this  be  proved  ?  Where  do  the 
powers  of  sensation  and  motion  reside?  How  is  this  shown?  257. 
Describe  the  situation  and  relations  of  the  medulla  oblongata.  What 
is  the  vital  knot  ?  258.  How  are  the  movements  of  respiration  regu- 
lated by  the  medulla  oblongata  ?  259.  Illustrate  the  automatic  action 
of  this  ganglion.     What  is  the  result  of  its  destruction  ? 

Chapter  V. — 260.  How  do  the  nerves  of  the  brain  differ  from  the 
spinal  nerves  ?  W'hich  are  the  most  important  ones?  WThat  parts  does 
the  trigeminal  nerve  supply?  What  is  its  function  ?  What  parts  are 
supplied  by  the  facial  nerve  ?  What  is  its  function  ?  How  may  it  be 
affected  by  exposure  to  cold  ?  261.  What  is  the  course  of  the  sciatic 
nerve?  What  is  the  cause  of  the  foot  "being  asleep"?  262.  What 
is   the  importance   of  reflex    action?      Give   illustrations  (foot-note). 

263.  Why  is  education  so  important  ?  WThy  are  habits  easily  formed 
in  the  young?     Why  do  they  need  the   guidance  of  older  persons? 

264.  WThy  is  it  important  that  the  brain  should  have  sufficient  exercise  ? 

265.  WThat  is  the  effect  of  over-exercise?  266.  Why  is  sleep  necessary? 
What  takes  place  during  sleep  ?  Why  do  we  wake  up  ?  What  is  the 
best  time  for  sleep?  Why?  How  much  sleep  is  necessary  ?  267.  What 
is  said  of  abuse  of  the  nervous  system,  and  its  danger? 

PART   V. 

Chapter  I. — 26S.  In  what  points  do  the  skin  and  mucous  mem- 
brane resemble  each  other  ?  What  are  the  functions  of  the  skin  ?  269. 
WThat  is  the  structure  of  the  skin  ?  The  epidermis  ?  The  derma  ? 
How  thick  is  the  skin  ?  270.  How  is  the  skin  connected  with  the  tis- 
sues beneath  it  ?     What  are  the  papillae  ?     Their  situation,  size,  and 


QUESTIONS.  287 

arrangement?  271.  What  causes  the  difference  of  complexion  in  dif- 
ferent persons  ?  What  is  an  albino  ?  What  seems  to  be  the  use  of  the 
pigment-cells?  272.  What  are  the  nails  ?  How  do  they  grow ?  What 
is  the  use  of  them?  273.  What  are  the  hairs?  How  do  they  grow  ? 
What  causes  the  difference  in  color  of  the  hair  in  different  persons  ? 
How  much  of  the  body  is  covered  with  hair?  274.  What  are  the  seba- 
ceous glands?  What  is  their  structure  ?  Where  are  they  situated  ? 
What  is  their  function  ?  What  is  the  result  when  their  openings  are 
obstructed?  275.  What  are  the  sweat-glands?  Where  are  they  situ- 
ated ?  What  is  their  structure?  How  large  are  they,  and  how  nu- 
merous ? 

Chapter  II.— 276.  What  is  the  effect  of  pressure  on  the  skin  ? 
What  diseases  may  be  produced  by  it  ?  277.  What  was  Lavoisier's  theory 
of  the  cause  of  animal  heat  ?  How  overthrown  ?  Liebig's  theory  ? 
What  objection  is  there  to  it?  What  is  believed  to  be  the  true  theory  ? 
278.  What  is  the  normal  temperature  of  the  human  body  ?  How  much 
may  it  vary  ?  279.  What  is  the  effect  of  a  great  fall  or  a  great  rise  in 
the  temperature  of  the  body  ?  What  external  temperatures  are  we 
often  exposed  to  ?  280.  What  is  the  effect  of  a  low  external  tempera- 
ture oh  the  body?  How  is  the  appetite  affected?  How  does  the  body 
accommodate  itself  to  such  a  temperature  ?  2S1.  What  is  the  effect 
upon  the  body  of  a  high  external  temperature?  282.  How  is  the  tem- 
perature of  the  body  regulated  by  the  perspiratory  glands  ?  283.  What 
is  the  insensible  perspiration?  What  is  its  daily  amount?  How  may 
it  be  immensely  increased  ?  284.  What  is  the  effect  of  exposure  to  dry 
heat?  285.  What  is  the  effect  of  exposure  to  moist  heat?  286.  What 
is  said  of  respiration  through  the  skin  ?  How  much  carbon  dioxide 
is  thrown  off  by  it  (foot-note)  ?  What  is  said  of  absorption  through  the 
skin  (foot-note)  ?  2S7.  How  does  the  skin  become  covered  with  im- 
purities? Why  should  these  be  removed  ?  288.  What  is  the  effect  of 
a  cold  bath  ?  How  long  should  the  bath  last  ?  289.  What  is  the  effect 
of  a  warm  bath  ?  Why  should  exposure  to  cold  be  avoided  after  it  ? 
290.  State  the  rules  for  bathing  and  the  reasons  for  them  ?  291.  How 
should  the  face  and  hands  be  cleaned?  What  is  the  objection  to  soap? 
How  is  "chapping"  produced?  How  may  it  be  prevented ?  What  is 
the  best  soap?  292.  What  causes  dandruff?  How  should  the  scalp 
be  cleaned?  What  is  said  about  cleaning  and  cutting  the  hair?  293. 
How  should  the  nails  be  cut  ?  Why  should  they  not  be  cut  close  to 
the  flesh  ?  What  causes  "hangnails"?  How  may  they  be  prevent- 
ed? What  causes  the  white  spots  on  nails?  294.  What  is  the  object 
of  clothing  ?  What  is  the  best  material  to  wear  next  the  skin  ?  Why  ? 
Why  is  linen  bad  for  this  purpose  ?    Why  should  the  under-clothing  be 


283  QUESTIONS. 

changed   at   night  ?     What   is   said    of  tight   and    high-heeled  shoes? 
What  are  the  general  rules  fur  the  .selection  of  clothing? 

TART    VI. 

CHAPTER  I. — 295.  Where  does  the  sense  of  touch  have  its  seat? 
How  do  the  nerves  end  in  the  papillae  of  the  skin  ?  296.  What  do  we 
learn  by  the  sense  of  touch  ?  How  does  the  sensitiveness  of  the  skin 
vary  in  different  parts  of  the  body  ?  How  is  this  shown?  What  is  the 
most  sensitive  part  (foot-note)?  297.  Can  the  extremes  of  sensation 
be  easily  distinguished  from  each  other?  What  is  said  of  deception 
through  the  senses?  Give  illustrations  (foot-note).  298.  What  rela- 
tion do  the  special  senses  bear  to  the  sense  of  touch  ?  What  pecul- 
iarity is  common  to  them?  299.  Where  is  the  sense  of  taste  located? 
How  are  the  nerves  of  taste  distributed  to  the  tongue?  How  do  they 
terminate?  How  do  we  taste?  300.  How  many  modifications  of  the 
sense  of  taste  are  there?  What  qualities  are  perceived  in  the  mouth 
by  the  sense  of  feeling?  Is  the  aroma  of  a  substance  tasted  or  smelt? 
How  may  this  be  determined?  301.  Why  do  substances  have  a  dif- 
ferent taste  on  the  front  and  back  of  the  tongue?  Give  illustrations. 
Why  does  the  sensation  of  taste  persist  for  a  time  after  the  substartce  has 
been  removed  ?  How  does  this  affect  the  detection  of  delicate  flavors? 
Why  do  we  smack  our  lips  when  tasting?  What  is  the  use  of  this 
sense?  302.  Where  does  the  sense  of  smell  reside?  What  is  the 
olfactory  nerve  ?  Its  situation  ?  How  much  of  any  substance  is  re- 
quired to  affect  the  sense  of  smell  ?  Why  do  we  sniff  at  odors  in  order 
to  appreciate  them  (foot-note)?  Illustrate  "the  occasional  difficulty 
of  distinguishing  between  the  sense  of  smell  and  that  of  feeling? 
303.  Illustrate  the  acuteness  of  this  sense  in  some  men  and  lower  ani- 
mals.    What  is  the  use  of  this  sense  ? 

Chapter  II. — 304.  What  kind  of  impressions  are  perceived  by  the 
sense  of  hearing?  305.  What  are  the  three  divisions  of  the  ear?  What 
is  the  use  of  the  external  ear?  Is  it  movable?  306.  What  is  the  tym- 
panum ?  How  do  the  air-waves  reach  it  ?  What  is  the  middle  ear  ? 
Its  situation  and  size?  What  is  the  Eustachian  tube?  Its  use?  307. 
Where  are  the  bones  of  the  ear?  How  many  are  there,  and  how  large? 
What  are  they  attached  to,  and  how  are  they  moved?  308.  What  is 
the  structure  of  the  internal  ear?  What  are  its  chief  parts,  and  what 
is  it  filled  with?  How  is  the  nerve  of  hearing  distributed ?  309.  How 
is  hearing  affected?  310.  Upon  what  do  the  different  qualities  of 
sound  depend?  311.  How  do  we  determine  the  direction  from  which 
sound  comes?  What  is  said  of  the  function  of  the  semi-circular  canals 
(foot-note)?     312.  What  is  ventriloquism?     How  are  its  effects  pro- 


QUESTIONS.  289 

duced?  313.  How  is  the  ear  protected  from  insects?  How  can  they 
be  removed  when  they  have  entered  the  ear  ?  What  is  said  of  the  use 
of  ear-scoops?  314.  How  may  colds  in  the  head  affect  the  hearing? 
How  may  permanent  deafness  be  caused  ? 

Chapter  III. — 315.  How  does  the  sense  of  sight  differ  greatly 
from  the  other  senses?  316.  What  is  light  believed  to  be?  How  i-ap- 
idly  does  it  travel?  Describe  the  wave  theory  of  light.  317.  How  is 
the  eye  protected?  318.  What  is  the  shape  of  the  eyeball?  Its  size? 
The  three  membranes?  Their  situation  and  structure?  319.  What  is 
the  vitreous  humor?  What  are  muscoe  volitantes  (foot-note)?  The 
crystalline  lens  ?  The  iris  ?  The  aqueous  humor  ?  320.  What  is  the 
use  of  the  sclerotic  coat  ?  Of  the  cornea  ?  Of  the  choroid  ?  What 
is  the  cause  of  "dazzling"?  What  peculiarity  have  the  eyes  of  albi- 
nos (foot-note) ?  321.  What  is  the  structure  of  the  retina?  What  is 
the  blind-spot  ?  How  may  its  existence  be  demonstrated  ?  Why  does 
it  not  interfere  with  sight?  322.  What  is  the  use  of  the  lens?  323. 
What  change  takes  place  in  the  eye  to  enable  us  to  see  either  near  or 
far  objects  at  will  ?  How  is  this  change  produced  ?  What  is  the  ciliary 
muscle  ?  Its  function  ?  324.  What  is  the  inner  limit  of  distinct  vision  ? 
The  farther  limit  ?  (In  healthy  eyes  it  is  practically  infinitely  distant.) 
325.  What  causes  the  color  of  the  iris?  What  are  the  functions  of  the 
iris  ?  What  are  spherical  and  chromatic  aberration  ?  How  are  they 
prevented  by  the  iris  ?  326.  How  is  it  shown  that  the  optic  nerve  con- 
veys only  the  sensation  of  light?  327.  Illustrate  the  persistence  of  im- 
pressions on  the  retina.  328.  What  is  meant  by  "color-blindness"? 
329.  Explain  near-sightedness  and  far-sightedness.  330.  How  is  the 
eyeball  moved?  331.  What  are  the  uses  of  the  eyelids,  eyebrows,  and 
eyelashes?  332.  What  are  the  tears?  Where  do  they  come  from, 
what  is  their  use,  and  what  becomes  of  them?  How  is  weeping  ex- 
plained ?  How  are  the  tears  prevented  from  overflowing  on  to  the 
cheeks  ?  333.  What  is  said  of  the  care  of  the  eyes  ?  Of  their  deli- 
cacy ?  Why  is  it  bad  to  strain  them  ?  Why  should  they  not  be  opened 
under  cold  water  (foot-note)  ?  What  abuses  of  the  eye  should  especial- 
ly be  avoided  ? 

PART   VII. 

334.   What  is  the  larynx?     Its  structure,    situation,  and  shape? 

335.  What  are  the  vocal  chords  ?     How  are  they  moved  (foot-note)? 

336.  How  is  the  voice  produced?  How  is  it  modulated?  337.  How 
is  the  larynx  commonly  abused  ?  What  effect  has  inflammation  of  the 
vocal  chords  upon  the  voice?  How  is  "  breaking"  of  the  voice  pro- 
duced ?  338.  Why  is  rest  necessary  when  the  vocal  chords  are  in- 
flamed ? 


INDEX. 


Abercrombie,  19S. 
Aberration,  chromatic,  265. 

spherical,  265. 
Abuse  of  nervous  system,  216. 
Accommodation,  function  of,  262. 
Adam's  apple,  272. 
Air,   amount    respired    with    each 
breath,  107. 

amount  respired  daily,  log. 

changed  by  respiration,  110. 

composition  of,  no,  113. 

contamination  of,  114,  115. 

impure,  in  houses,  115. 

purification  of,  by  plants,  114. 

watery  vapor  in,  113. 
Albinos,  eyes  of,  259. 
Albumen  of  blood,  95. 

of  food,  47. 
Alcohol,  diseases  due  to,  76. 

effects  of,  74. 

effect  of,  on  youth,  76. 

endurance  diminished  by,  76. 
Alimentary  canal,  57. 

muscles  of,  59. 
Anatomical  element  defined,  1. 
Anatomy  defined,  1. 
Animal  heat,  223. 

cause  of,  225. 

theories  of,  224. 
Anterior   nerve-root,    division   of, 

187. 
Aorta,  130,  145. 
Apoplexy,  190. 
Apparatus  defined,  2. 
Appendix  vermiformis,  80. 
Aqueous  humor,  258. 


Aroma,  241. 
Arteries,  120. 

compression  of  large,  161. 

rapidity  of  current  in,  142. 

structure  of,  136. 

behavior  of,  when  cut,  155. 
Artery,  brachial,  147. 

carotid,  147. 

femoral,  146. 

formation  of  clot  in,  158. 

pulmonary,  130,  149. 

radial,  147. 

ulnar,  147. 

venous  blood  in,  143. 

vertebral,  147. 
Artificial  respiration,  122. 
Asphyxia,  120. 
Asthma,  104. 
Auditory  nerve,  249. 
Auricles,  128. 
Automatic  actions,  193. 
Axis-cylinder,  167. 

Bacteria,  118. 
Banting  system,  47. 
Bath,  effect  of  cold,  231. 

warm,  232. 
Bathing,  rules  for,  232. 
Beaumont,  64. 
Bell,  Sir  Charles,  186. 
Bernard,  Claude,  55. 
Biceps,  disadvantageous  action  of, 

34- 
Bile,  83. 

function  of,  S4,  85. 
Black-heads,  222. 


2Q3 


JXDEX. 


Bleeding.     (See  Hemorrhage.) 
Blind  spot  of  eye,  260. 
Blood,  93. 

albumen  of,  95. 

1  amount  of,  97. 

changes    of,    during    digestion, 
91. 

changes  of,  during  respiration, 
in. 

coagulation  of,  96,  97,  154. 

distribution  of,  145. 

fibrin  of,  95. 

oxygen  in,  97. 

plasma  of,  95. 

rapidity  of,  142. 

serum  of,  96. 

varying  color  of,  9S,  1 12. 
Blood-corpuscles,  function  of,  112. 

red,  93. 

white,  95. 
Blood-vessels,  136. 

communicating,  141. 
Blushing,  178. 
Body,  effect  of  cold  on,  226. 

effect  of  heat  on,  227. 

minute  structure  of,  3. 

temperature  of,  225. 

temperature  of,  how  regulated, 
228. 
Bone  at  different  ages,  10. 

composition  of,  9. 

minute  structure  of,  12. 

living  and  dead,  9. 

renewal  of,  14. 

extremities  and  shaft  of,  II. 
Bones,  injuries  of,  25. 

number  of,  15. 

of  ear,  248. 

ossification  of,  15. 

uses  of,  9. 

varieties  of,  II. 
Brachial  artery,  147. 
Brain,  194. 

convolutions  of,  196. 

disease  of,  200. 

hemispheres  of,  196. 

importance  of  exercising,  213. 

injuries  of,  199,  201. 

over-exercise  of,  214. 

size  of,  198. 

smaller  ganglia  of,  204. 

softening  of,  200. 


Breath,    organic    matter   of,    in, 
115. 
shortness  of,  152,  163,  206. 
Bronchi,  100. 

Cacum,  80. 
Callous  skin,  223. 
Calvin  Edson,  89. 
Capillaries,  137. 

pressure  in,  141. 

rapidity  of  current  in,  142. 

size  of,  138. 
Carbon    dioxide,    theories   about, 
no. 

where  formed,  112. 
Carbonaceous  foods,  45. 
Cardiac  orifice  of  stomach,  62. 
Care  of  injured  persons,  27. 
Carotid  artery,  147. 
Cartilage,  23. 
Cartilages  of  trachea,  100. 
Casein,  47. 
Cauda  equina,  183. 
Cell,  4. 
Cells,  division  of,  6. 

epidermal,  59. 

epithelial,  59. 

growth  of,  6. 

living  and  dead,  5. 

nerve,  167. 

selection  by,  5. 

size  of,  5. 

vicarious  action  of,  8. 
Cerebellum,  diseases  of,  203. 

function  of,  202. 

removal  of  pigeon's,  202. 

size  of,  202. 

structure  of,  201. 
Cerebro-spinal  system,  166. 
Cerebrum,  195. 

function  of,  197,  201. 

removal  of  pigeon's,  199. 

size  of,  198. 

structure  of,  196. 
Chabert,  229. 
Chapped  hands,  233. 
Chest,  natural  shape  of,  21. 
Chloral,  75. 
Chloroform,  75. 
Choroid  coat,  257. 

function  of,  259. 
Chromatic  aberration,  265. 


INDEX. 


293 


Chyle,  90. 
Chyme,  79. 
Cilia,  103. 

action  of,  108. 
Ciliary  muscle,  262. 
Ciliated  epithelium,  103. 
Circulation,  125,  130. 

disorders  of,  150. 

general,  127. 

obstruction  of,  150. 

pulmonary,  127. 

rapidity  of,  144. 
Clot,  96. 
Clothing,  235. 
Coagulation  of  blood,  96. 

conditions  of,  154. 
Cochlea,  249. 
Coffee,  77. 
Cold  arrests  bleeding,  156. 

bath,  effect  of,  231. 

effect  of,  on  body,  226. 
Colds,  cause  of,  181. 

in  the  head,  danger  of,  252. 
Color-blindness,  266. 
Combustion,   pollution  of  air  by, 

115. 
Complexion,  219. 
Compress,  graduated,  162. 
Compression  of  wounds,  157. 
Condiments,  72. 
Confectionery,  77. 
Connective  tissue,  29. 
Contagious  diseases,  117. 
Convolutions  of  brain,  196. 
Cooking,  49. 

Co-ordination,  organs  of,  164. 
Cornea,  function  of,  259. 

structure  of,  256. 
Corns,  223. 
Crying,  269. 
Crystalline  lens,  258. 

function  of,  261. 
Curvature  of  spine,  38. 
Cuticle,  cutis,  217. 
Cuvier,  198. 
Cysticercus  cellulose,  7S. 

Dandruff,  234. 

Deafness,  frequent  cause  of,  253. 

Deception  by  the  senses,  238. 

Derma,  218. 

Diaphragm,  105. 


Diffusion  of  gases,  108. 
Digestion,  blood  during,  91. 

intestinal,  79. 

nervous  control  of,  180. 

stomach,  57,  63. 

time  required  for,  72. 
Digestive  apparatus,  50. 
Disinfectants,  118. 
Dislocations,  26,  27. 
Dissipation,  216. 
Draughts,  116,  176,  180. 
Drink,  73. 
Dropsy,  151,  152. 
Drowned,    resuscitation    of     the, 

121. 
Drowning,  121. 
Drum  of  ear,  247. 
Duodenum,  81. 
Dupuytren,  198. 

Ear,  bones  of,  24S. 

care  of,  252. 

drum  of,  247. 

external,  246. 

insects  in,  252. 

internal,  249. 

middle,  247. 

muscles  of,  247. 

-scoops,  252. 
Ear-wax,  252. 

Eating,  rules  for,  69-71,  78. 
Education,  211. 
Element,  anatomical,  1. 
Emotion,  effects  of,  178. 
Epidermal  cells,  59. 
Epidermis,  59,  217,  219. 
Epiglottis,  102. 
Epithelium,  59. 

ciliated,  103. 
Ether,  75. 

the,  254. 
Eustachian  tube,  248. 

inflammation  of,  253. 
Exercise,  39. 

of  nervous  system,  213,  214. 

rules  for,  41. 
Exhaustion,  danger  of,  40, 
Expiration,  force  of,  107. 

mechanism  of,  106. 
External  auditory  canal,  252. 
External  ear,  246. 
Extremities,  wounds  of,  160. 


294 


INDEX. 


Eye,  blind  spot  of,  260. 
situation  of,  255. 

Eyeball,  muscles  of,  267. 

structure  of,  255. 
Eyebrows,  lashes,  lids,  268. 
Eyes,  care  of,  270. 

opening  of,  under  water,  271. 

straining  of,  270. 

Face,  washing  of,  233. 
Facial  nerve,  209. 
Fainting,  162. 
Far-sight,  267. 
Fat,  46. 

craving  for,  in  winter,  226. 
Fatigue,  37. 
Femoral  artery,  146. 
Fiber,  3. 
Fibrin  of  blood,  95. 

of  food,  47. 
Fibrous  tissue,  3. 
Fire-king,  229. 
Fireplace  as  ventilator,  116. 
Fluid,  synovial,  24. 
Follicles,  hair,  221. 
Food,  absorption  of,  86. 

carbonaceous,  45. 

choice  of,  72. 

classification  of,  43. 

daily  amount  of,  49. 

inorganic  elements  of,  45. 

necessity  of,  43. 

nitrogenous,  47. 

non-nitrogenous,  45. 

parasites  in,  78. 

variety  of,  48. 
Fracture,  green-stick,  II. 

results  of,  26. 
Fractures,  25. 

healing  of,  27. 
Freezing,  225. 

Frog's  foot,  circulation  in,  142. 
Frontal  sinuses,  20. 
Function  defined,  2. 

Ganglia,  nervous,  168. 

sympathetic,  175. 
Gangrene,  154. 
Garotte,  207. 
Gases,  diffusion  of,  108. 
Gastric  juice,  amount  of,  66. 

composition  of,  66. 


( '.a^tric  juice,  secretion  of,  65. 
General  circulation,  127. 
Glands,  lachrymal,  26S. 

lymphatic,  88. 

nervous  supply  of,  178. 

salivary,  54. 

sebaceous,  221. 

sweat,  222. 
Glottis,  101,  272. 
Glucose,  46. 

Graduated  compress,  162. 
Granular  matter,  5. 
Gray  matter,  function  of,  171. 

structure  of,  167. 
Great  pouch  of  stomach,  62. 
Green-stick  fracture,  II. 
Gymnastics,  39. 

Habits,  formation  of,  212. 
Haemoglobin,  112. 
Haemorrhage,  155. 

artificial  arrest  of,  156. 

compression  for,  157. 

natural  arrest  of,  155. 

permanent  arrest  of,  158. 
Hair,  220. 

cutting  of,  225. 
Handkerchief,  knotted,  161. 
Hands,  chapping  of,  233. 

washing  of,  233. 
Hang-nails,  235. 
Hausmann,  198. 
Hearing,  sense  of,  246. 
Heart,  126. 

blood-vessels    connected    with, 
130. 

cavities  of,  127. 

contraction  of,  133. 

disease  of,  151. 

rapidity  of  contraction  of,  134. 

sounds  of,  134. 

two  sides  of,  127. 

valves  of,  128. 

voluntary  arrest  of,  135. 
Heart-disease,  detection  of,  154. 
Heat,  effect  of,  on  body,  227. 

exposure  to  dry,  229. 

exposure  to  moist,  229. 
Hemispheres  of  brain,  196. 
Hiccough,  106. 
Homologous  bones,  23. 
I  Humor,  aqueous,  258,, 


INDEX. 


295 


Humor,  vitreous,  257. 
Hunger,  70. 
Hygiene  defined,  I. 

Impure  air,  115. 
Inactivity,  muscular,  38. 
Indigestion,  67. 
Injured  persons,  care  of,  27. 
Injuries  of  bones  and  joints,  25. 
Inorganic  elements  of  food,  45. 
Insects  in  the  ear,  252. 
Insensible  perspiration,  228. 
Inspiration,  force  of,  107. 

mechanism  of,  105. 
Internal  ear,  249. 
Intestinal  digestion,  79. 

juices,  85. 

villi,  87. 
Intestine,  large,  80. 

muscles  of,  80. 

small,  79. 
Intoxication,  74. 
Involuntary  muscles,  31. 
Iris,  258. 

color  of,  264. 

function  of,  265. 

nervous  supply  of,  177. 
Irritability,  muscular,  35. 

Jaundice,  84. 
Joints,  23. 

injuries  of,  26. 
Jugular  veins,  148. 
Juice,  gastric,  65. 

intestinal,  85. 

pancreatic,  82. 

Knotted  handkerchief,  use  of,  161. 

Labyrinth,  249. 
Lachrymal  gland,  268. 
Lacteals,  86,  88,  90. 
Large  intestine,  80. 
Larynx,  100,  272. 

abuse  of,  274. 

care  of,  275. 

movable  cartilages  of,  273. 
Latissimus  dorsi,  33. 
Lavoisier,  224. 
Lead  in  candy,  78. 
Lens,  258. 

function  of,  261. 


Lens,  varying  shape  of,  263. 

Liebig,  224. 

Ligaments,  24. 

Ligatures,  use  of,  158. 

Light,  254. 

Limbs,  number  of  bones  in,  22. 

Limit  of  distinct  vision,  263. 

Liver,  82. 

Liver-sugar,  82. 

Living  skeleton,  89. 

Lungs,  102. 

blood-vessels  of,  104. 

change  of  air  in,  108. 

minute  structure  of,  103. 

serous  membrane  of,  104. 
Lymph,  88. 
Lymphatic  glands,  88. 

Magendie,  186. 
Malarial  fevers,  117. 
Marrow,  12. 
Masseter  muscle,  53. 
Mastication,  50,  69. 
Medulla  oblongata,  205. 

automatic  action  of,  206. 
Membrane,  mucous,  57. 

serous,  60. 

synovial,  24. 
Microscopic  organisms,  117,  1 18. 
Middle  ear,  247. 
Minute  structure  of  body,  3. 
Mouth,  watering  of  the,  55,  178. 
Mucous  membrane,  57. 
Mumps,  54. 
Muscae  volitantes,  257. 
Muscle,  ciliary,  262. 

minute  structure  of,  31. 
Muscles,  29. 

contraction  of,  32. 

of  eyeball,  267. 

function  of,  31. 

involuntary,  31. 

size  of,  33. 

voluntary,  29. 
Muscular  contraction,  force  of,  34. 

contraction,  sound  of,  53. 

contraction,  waste  during,  37. 

inactivity,  38. 

irritability,  35. 

overwork,  37. 

sense,  35,  36. 

strength,  feats  of,  40. 


296 


INDEX. 


Mustard,  73. 

Myelin,  1O7. 

Nails,  220. 

care  of,  235. 
Narcotic  poisons,  75. 
Narcotism,  symptoms  of,  75. 
Nasal  passages,  99. 
Near-sight,  267. 
Nerve,  auditory,  249. 

division  of  anterior  root  of,  187. 

division  of  posterior  root  of,  188. 

effect  of  dividing,  185. 

facial,  209. 

olfactory,  243. 

optic,  260. 

sciatic,  210. 

trigeminal,  208. 
Nerve-cells,  167. 
Nerve-centers,  168. 
Nerve-current,  nature  of,  169,  172. 

rapidity  of,  170. 
Nerve-fibers,  166. 

function  of,  168,  169. 
Nerves,  electrical  current  in,  169, 
172. 

exhaustion  of,  171. 

sensations  referred  to  extremity 
of,  190. 

structure  of,  168. 

vaso-motor,  145,  179. 
Nervous  system,  abuse  of,  216. 

divisions  of,  164. 

education  of,  211. 
Nervous  tissue,  166. 
Nitrogenous  foods,  47. 
Non-nitrogenous  foods,  45. 
Nose,  structure  of,  99. 
Nucleolus,  5. 
Nucleus,  5. 
Nystagmus,  259. 

GEsophagus,  57,  60. 

Olfactory  nerve,  243. 

Opium,  75. 

Optic  nerve,  260. 

Optic  nerves,  origin  of,  204. 

Orbit  of  eye,  255. 

Organ  of  speech,  272. 

Organic  matter  of  breath,  III,  115. 

Organisms,  microscopic,  117,  118. 

Organs  of  co-ordination,  164. 


Organs  of  motion,  9. 

of  perception,  237. 

of  protection,  217. 

of  repair,  42. 
Ossification  of  bones,  15. 
Out-door  sports,  39. 
Overeating,  69. 
( her-exercise  of  brain,  214. 
Overwork,  muscular,  37. 
Oxygen,  necessity  of,  97. 
Oxyhemoglobin,  1 12. 

Pancreas,  81. 

functions  of,  82. 
Pancreatic  juice,  82. 
Papillae  of  skin,  219. 

structure  of,  237. 
Paraplegia,  192. 
Parasites  in  food,  78. 
Parotid  glands,  54. 
Pepper,  72. 
Pepsin,  76. 

Perception,  organs  of,  237. 
Pericardium,  126. 
Periosteum,  12. 

uses  of,  13. 
Peritonaeum,  86. 
Perspiration,  amount  of,  228. 
Perspiratory  glands,  222. 
Phantom  limbs,  191. 
Pharynx,  60. 
Physiology  defined,  I. 
Pigeon,  removal  of  cerebellum  of, 
202. 

removal  of  cerebrum  of,  199. 
Pigment-cells,  219. 
Plain  food,  advantages  of,  71. 
Plants,  respiration  of,  114. 
Plasma,  95. 
Pleura,  105. 
Pleurisy,  105. 
Portal  vein,  89,  148. 
Posterior  nerve-root,   division   of, 

18S. 
Protection,  organs  of,  217. 
Proteids,  47. 
Protoplasm,  4,  5. 
Proud  flesh,  7. 
Pulmonary  artery,  130,  149. 

circulation,  127. 

lobule,  103. 

veins,  130,  149. 


INDEX. 


297 


Pulmonary  vesicle,  103. 
Pulse,  cause  of,  136. 

rapidity  of,  135. 

situation  of,  137. 

voluntary  control  of,  135. 
Pupil,  contraction  of,  176. 
Pylorus,  62. 

Eadial  artery,  147. 
Red  blood-corpuscles,  93. 
Reflex  action,  170,  191,  210. 
Respiration,  99. 

artificial,  122. 
Rest  for  muscles,  40. 
Resuscitation    of    the     drowned, 

121. 
Retina,  257. 

effect  of  shocks  on,  265. 

persistence  of  impressions   on, 
266. 

structure  of,  260. 
Ribs,  20. 

cartilages  of,  21. 

motion  of,  21. 
Rods  and  cones  of  retina,  260. 
Roots  of  spinal  nerves,  1S6. 
Rules  for  bathing,  232. 

for  dress,  236. 

for  eating,  78. 

for  exercise,  41. 

for  entering  sick-room,  119. 

St.  Martin,  64. 
Saliva,  54. 

amount  of,  56. 

use  of,  55. 
Salivary  glands,  54. 
Salt,  44. 
Sartorius,  33. 

Savages,  acute  senses  of,  244. 
Scalp,  care  of,  234. 
Schwann,    white     substance     of, 

167. 
Sciatic  nerve,  210. 
Sclerotic  coat,  255. 

function  of,  259. 
Sebaceous  glands,  221. 
Semicircular  canals,  249-251. 
Sensation,  170. 

divisions  of,  184. 
Sense,  muscular,  35. 

of  hearing,  246. 


Sense  of  sight,  254. 

of  smell,  243. 

of  taste,  240. 

of  touch,  237. 
Senses,  deception  by,  238. 
Serous  membrane,  60. 
Serum  of  blood,  96. 
Sewer-air,  119. 
Shoes,  236. 
Shortness    of    breath,     103,    152, 

206. 
Sick-room,    rules     on     entering, 

119. 
Sight,  sense  of,  254. 
Sinuses,  frontal,  20. 
Skin,  absorption  through,  230. 

effects  of  pressure  on,  223. 

impurities  on,  231. 

respiration  through,  230. 

structure  of,  217. 
Skull,  18,  19. 
Sleep,  214. 
Small  intestine,  79. 
Smell,  sense  of,  243. 

use  of,  52,  245. 
Sniffing,  244. 
Soap,  233,  234. 
Solar  plexus,  175. 
Sound,  determination  of  source  of, 
250. 

qualities  of,  250. 
Sounds  of  heart,  134. 
Special  senses,  239. 
Speech,  organ  of,  272. 
Spherical  aberration,  265. 
Spinal  canal,  17. 
Spinal  cord,  183. 

cord,  crossing  of  fibers  in,  189. 

cord,  diseases  of,  192. 

cord,  reflex  action  of,  191. 
Spinal  nerves,  184. 

nerves,  roots  of,  186. 

nerves,  two  kinds  of  fibers  of, 
189. 
Spine,  15. 

cartilages  of1,  15,  18. 

curvature  of,  38. 

mobility  of,  17. 
Spleen,  91. 

function  of,  92. 
Splints,  28. 
Sprains,  27. 


298 


INDEX. 


Stapedius,  33. 
Starch,  45. 

Stomach,    appearance   of,    during 
digestion,  67. 

foods  digested  in,  63. 

interior  of,  65. 

movements  of,  66. 

structure  of,  60. 
Stomach-digestion,  57,  63. 

time  of,  6S. 
Strength,  muscular,  40. 
Striation,  31. 
Styptics,  156. 
Suffocation,  120. 
Sugar,  46. 
Sunstroke,  226. 
Sutures,  19. 
Swallowing,  50,  60. 
Sweat-glands,  222. 
Sweet-bread,  81. 
Sympathetic  ganglia,  175. 
Sympathetic    nerves,   division   of, 

177. 

nerves,  peculiarity  of,  172. 

nerves,  sluggish  action  of,  175. 
Sympathetic  system,  166,  174. 

system,  effect  of  cold  on,  180. 

system,  exhaustion  of,  181. 
Synovial  fluid,  24. 

membrane,  24. 
System  defined,  2. 

Tape-worm,  78. 

Taste,  modifications  of,  240. 

peculiarities  of,  241. 

sense  of,  239,  240. 

use  of,  in  eating,  52. 
Tea,  77. 
Tears,  268. 
Teeth,  52. 

care  of,  56. 
Temperature  of  body,  225. 

of  body,  how  regulated,  228. 
Tendons,  33. 
Thoracic  duct,  89. 
Tight  lacing,  effect  of,  21. 
Tissue,  connective,  29. 

defined,  I. 

fibrous,  3. 
Tobacco,  77. 
Toilet-soaps,  234. 
Tongue,  nerves  of,  240. 


Touch,  delicacy  of,  238. 

sense  of,  237. 
Townsend,  Colonel,  135. 
Trachea,  100. 
Trichina  spiralis,  78. 
Trigeminal  nerve,  208. 
Tubercula  quadrigemina,  204. 
Tympanum,  248. 

Ulnar  artery,  147. 

nerve,  190. 
Urea,  42. 

Valves  of  heart,  128. 

of  heart,  peculiar,  131. 

of  veins,  140. 
Vaso-motor  nerves,  145,  179. 
Vein,  arterial  blood  in,  143. 

behavior  of,  when  cut,  155. 

portal,  89,  148. 
Veins,  120. 

circulation  in,  139. 

jugular,  148. 

pulmonary,  130,  149. 

rapidity  of  current  in,  143. 

structure  of,  138. 

valves  of,  140. 
Venae  cavae,  130,  138,  148. 
Ventilation,  115. 
Ventricles,  128. 
Ventriloquism,  251. 
Vertebra,  15. 
Vertebral  artery,  147. 
Vestibule,  249. 
Villi,  87. 

pumping  action  of,  90. 
Vision,  limit  of  distinct,  263. 
Vital  knot,  205,  207. 
Vitreous  humor,  257. 
Vocal  chords,  102,  272. 

congestion  of,  274. 
Voice,  breaking  of,  275. 

modulation  of,  274. 

production  of,  273. 
Voluntary  muscles,  29. 

Warm  bath,  effect  of,  232. 
Warts,  223. 

Washing  hands  and  face,  233. 
Waste  during   muscular  contrac- 
tion, 37. 
Water,  44. 


INDEX. 


299 


Water,  paramount  necessity  of,  48. 
Wave  theory  of  light,  254. 
Weeping,  269. 
White  blood-corpuscles,  95. 
White  matter,  166. 


White  matter,  function  of,  169. 

Windpipe,  100. 

Wounds,  compression  of,  157. 

of  extremities,  160. 

healing  of,  7. 


THE    END. 


'4 


W 


